Undefined array key "connect_nulls"

I have the same error and if you google it there are a view others.

Warning: Undefined array key "connect_nulls" in Drupal\charts\Plugin\views\style\ChartsPluginStyleChart->render() (line 336 of /...//modules/contrib/charts/src/Plugin/views/style/ChartsPluginStyleChart.php)

#0 /...//core/includes/bootstrap.inc(166): _drupal_error_handler_real()
#1 /...//modules/contrib/charts/src/Plugin/views/style/ChartsPluginStyleChart.php(336): _drupal_error_handler()
#2 /...//core/modules/views/src/Plugin/views/display/DisplayPluginBase.php(2177): Drupal\charts\Plugin\views\style\ChartsPluginStyleChart->render()
#3 /...//core/modules/views/src/ViewExecutable.php(1593): Drupal\views\Plugin\views\display\DisplayPluginBase->render()
#4 /...//core/modules/views/src/Plugin/views/display/Block.php(133): Drupal\views\ViewExecutable->render()
#5 /...//core/modules/views/src/ViewExecutable.php(1690): Drupal\views\Plugin\views\display\Block->execute()
#6 /...//core/modules/views/src/Element/View.php(81): Drupal\views\ViewExecutable->executeDisplay()
#7 [internal function]: Drupal\views\Element\View::preRenderViewElement()
#8 /...//core/lib/Drupal/Core/Security/DoTrustedCallbackTrait.php(113): call_user_func_array()
#9 /...//core/lib/Drupal/Core/Render/Renderer.php(870): Drupal\Core\Render\Renderer->doTrustedCallback()
#10 /...//core/lib/Drupal/Core/Render/Renderer.php(432): Drupal\Core\Render\Renderer->doCallback()
#11 /...//core/lib/Drupal/Core/Render/Renderer.php(248): Drupal\Core\Render\Renderer->doRender()
#12 /...//core/lib/Drupal/Core/Template/TwigExtension.php(484): Drupal\Core\Render\Renderer->render()
#13 /...//sites/default/files/php/twig/67862c3a8fea6_viewfield-item.html.twig_K-GaYPZNWd_RyzYVAcCyBbYFE/jdIHjz7GsR44U3CXMdLcawygTY3-F3jzlkYV39vuJcE.php(94): Drupal\Core\Template\TwigExtension->escapeFilter()
#14 /var/www/vendor/twig/twig/src/Template.php(431): __TwigTemplate_2805eb420b5100c429475342ec366984->block_content()
#15 /...//sites/default/files/php/twig/67862c3a8fea6_viewfield-item.html.twig_K-GaYPZNWd_RyzYVAcCyBbYFE/jdIHjz7GsR44U3CXMdLcawygTY3-F3jzlkYV39vuJcE.php(77): Twig\Template->yieldBlock()
#16 /var/www/vendor/twig/twig/src/Template.php(387): __TwigTemplate_2805eb420b5100c429475342ec366984->doDisplay()
#17 /var/www/vendor/twig/twig/src/Template.php(343): Twig\Template->yield()
#18 /var/www/vendor/twig/twig/src/Template.php(358): Twig\Template->display()
#19 /var/www/vendor/twig/twig/src/TemplateWrapper.php(35): Twig\Template->render()
#20 /...//core/themes/engines/twig/twig.engine(33): Twig\TemplateWrapper->render()
#21 /...//core/lib/Drupal/Core/Theme/ThemeManager.php(348): twig_render_template()
#22 /...//core/lib/Drupal/Core/Render/Renderer.php(491): Drupal\Core\Theme\ThemeManager->render()
#23 /...//core/lib/Drupal/Core/Render/Renderer.php(248): Drupal\Core\Render\Renderer->doRender()
#24 /...//core/modules/views/src/Plugin/views/field/EntityField.php(974): Drupal\Core\Render\Renderer->render()
#25 /...//core/modules/views/src/Plugin/views/field/FieldPluginBase.php(1214): Drupal\views\Plugin\views\field\EntityField->render_item()
#26 /...//core/modules/views/views.theme.inc(238): Drupal\views\Plugin\views\field\FieldPluginBase->advancedRender()
#27 [internal function]: template_preprocess_views_view_field()
#28 /...//core/lib/Drupal/Core/Theme/ThemeManager.php(261): call_user_func_array()
#29 /...//core/lib/Drupal/Core/Render/Renderer.php(491): Drupal\Core\Theme\ThemeManager->render()
#30 /...//core/lib/Drupal/Core/Render/Renderer.php(248): Drupal\Core\Render\Renderer->doRender()
#31 /...//core/modules/views/src/Plugin/views/field/FieldPluginBase.php(1796): Drupal\Core\Render\Renderer->render()
#32 /...//core/modules/views/src/Plugin/views/style/StylePluginBase.php(769): Drupal\views\Plugin\views\field\FieldPluginBase->theme()
#33 [internal function]: Drupal\views\Plugin\views\style\StylePluginBase->elementPreRenderRow()
#34 /...//core/lib/Drupal/Core/Security/DoTrustedCallbackTrait.php(113): call_user_func_array()
#35 /...//core/lib/Drupal/Core/Render/Renderer.php(870): Drupal\Core\Render\Renderer->doTrustedCallback()
#36 /...//core/lib/Drupal/Core/Render/Renderer.php(432): Drupal\Core\Render\Renderer->doCallback()
#37 /...//core/lib/Drupal/Core/Render/Renderer.php(248): Drupal\Core\Render\Renderer->doRender()
#38 /...//core/modules/views/src/Plugin/views/style/StylePluginBase.php(708): Drupal\Core\Render\Renderer->render()
#39 /...//core/modules/views/src/Plugin/views/style/StylePluginBase.php(574): Drupal\views\Plugin\views\style\StylePluginBase->renderFields()
#40 /...//core/modules/views/src/Plugin/views/style/StylePluginBase.php(462): Drupal\views\Plugin\views\style\StylePluginBase->renderGrouping()
#41 /...//core/modules/views/src/Plugin/views/display/DisplayPluginBase.php(2177): Drupal\views\Plugin\views\style\StylePluginBase->render()
#42 /...//core/modules/views/src/ViewExecutable.php(1593): Drupal\views\Plugin\views\display\DisplayPluginBase->render()
#43 /...//core/modules/views/src/Plugin/views/display/Block.php(133): Drupal\views\ViewExecutable->render()
#44 /...//core/modules/views/src/ViewExecutable.php(1690): Drupal\views\Plugin\views\display\Block->execute()
#45 /...//core/modules/views/src/Element/View.php(81): Drupal\views\ViewExecutable->executeDisplay()
#46 [internal function]: Drupal\views\Element\View::preRenderViewElement()
#47 /...//core/lib/Drupal/Core/Security/DoTrustedCallbackTrait.php(113): call_user_func_array()
#48 /...//core/lib/Drupal/Core/Render/Renderer.php(870): Drupal\Core\Render\Renderer->doTrustedCallback()
#49 /...//core/lib/Drupal/Core/Render/Renderer.php(432): Drupal\Core\Render\Renderer->doCallback()
#50 /...//core/lib/Drupal/Core/Render/Renderer.php(248): Drupal\Core\Render\Renderer->doRender()
#51 /...//core/lib/Drupal/Core/Template/TwigExtension.php(484): Drupal\Core\Render\Renderer->render()
#52 /...//sites/default/files/php/twig/67862c3a8fea6_viewfield-item.html.twig_K-GaYPZNWd_RyzYVAcCyBbYFE/jdIHjz7GsR44U3CXMdLcawygTY3-F3jzlkYV39vuJcE.php(94): Drupal\Core\Template\TwigExtension->escapeFilter()
#53 /var/www/vendor/twig/twig/src/Template.php(431): __TwigTemplate_2805eb420b5100c429475342ec366984->block_content()
#54 /...//sites/default/files/php/twig/67862c3a8fea6_viewfield-item.html.twig_K-GaYPZNWd_RyzYVAcCyBbYFE/jdIHjz7GsR44U3CXMdLcawygTY3-F3jzlkYV39vuJcE.php(77): Twig\Template->yieldBlock()
#55 /var/www/vendor/twig/twig/src/Template.php(387): __TwigTemplate_2805eb420b5100c429475342ec366984->doDisplay()
#56 /var/www/vendor/twig/twig/src/Template.php(343): Twig\Template->yield()
#57 /var/www/vendor/twig/twig/src/Template.php(358): Twig\Template->display()
#58 /var/www/vendor/twig/twig/src/TemplateWrapper.php(35): Twig\Template->render()
#59 /...//core/themes/engines/twig/twig.engine(33): Twig\TemplateWrapper->render()
#60 /...//core/lib/Drupal/Core/Theme/ThemeManager.php(348): twig_render_template()
#61 /...//core/lib/Drupal/Core/Render/Renderer.php(491): Drupal\Core\Theme\ThemeManager->render()
#62 /...//core/lib/Drupal/Core/Render/Renderer.php(248): Drupal\Core\Render\Renderer->doRender()
#63 /...//core/lib/Drupal/Core/Template/TwigExtension.php(484): Drupal\Core\Render\Renderer->render()
#64 /...//sites/default/files/php/twig/67862c3a8fea6_viewfield.html.twig_jbKm3zPYyIvhEMWL4zUWqEZyo/vNiMG7oVYamrdfqXrJ_KL-xTZwfetLbMnBVYbNa_niM.php(90): Drupal\Core\Template\TwigExtension->escapeFilter()
#65 /var/www/vendor/twig/twig/src/Template.php(387): __TwigTemplate_17ba97cd14306990d974735319171a51->doDisplay()
#66 /var/www/vendor/twig/twig/src/Template.php(343): Twig\Template->yield()
#67 /var/www/vendor/twig/twig/src/Template.php(358): Twig\Template->display()
#68 /var/www/vendor/twig/twig/src/TemplateWrapper.php(35): Twig\Template->render()
#69 /...//core/themes/engines/twig/twig.engine(33): Twig\TemplateWrapper->render()
#70 /...//core/lib/Drupal/Core/Theme/ThemeManager.php(348): twig_render_template()
#71 /...//core/lib/Drupal/Core/Render/Renderer.php(491): Drupal\Core\Theme\ThemeManager->render()
#72 /...//core/lib/Drupal/Core/Render/Renderer.php(504): Drupal\Core\Render\Renderer->doRender()
#73 /...//core/lib/Drupal/Core/Render/Renderer.php(504): Drupal\Core\Render\Renderer->doRender()
#74 /...//core/lib/Drupal/Core/Render/Renderer.php(504): Drupal\Core\Render\Renderer->doRender()
#75 /...//core/lib/Drupal/Core/Render/Renderer.php(248): Drupal\Core\Render\Renderer->doRender()
#76 /...//core/lib/Drupal/Core/Template/TwigExtension.php(484): Drupal\Core\Render\Renderer->render()
#77 /...//sites/default/files/php/twig/67862c3a8fea6_taxonomy-term.html.twig_w2ZB8F9Rtc_8FNFZ9b45l6QNr/ljPIUo-_dJ38wTy7D8NgQVja92-OCxR8uvX51_vLJk4.php(72): Drupal\Core\Template\TwigExtension->escapeFilter()
#78 /var/www/vendor/twig/twig/src/Template.php(387): __TwigTemplate_bd68ef3e5b521e89806a5a6eba79c513->doDisplay()
#79 /var/www/vendor/twig/twig/src/Template.php(343): Twig\Template->yield()
#80 /var/www/vendor/twig/twig/src/Template.php(358): Twig\Template->display()
#81 /var/www/vendor/twig/twig/src/TemplateWrapper.php(35): Twig\Template->render()
#82 /...//core/themes/engines/twig/twig.engine(33): Twig\TemplateWrapper->render()
#83 /...//core/lib/Drupal/Core/Theme/ThemeManager.php(348): twig_render_template()
#84 /...//core/lib/Drupal/Core/Render/Renderer.php(491): Drupal\Core\Theme\ThemeManager->render()
#85 /...//core/lib/Drupal/Core/Render/Renderer.php(504): Drupal\Core\Render\Renderer->doRender()
#86 /...//core/lib/Drupal/Core/Render/Renderer.php(248): Drupal\Core\Render\Renderer->doRender()
#87 /...//core/lib/Drupal/Core/Template/TwigExtension.php(484): Drupal\Core\Render\Renderer->render()
#88 /...//sites/default/files/php/twig/67862c3a8fea6_views-view.html.twig_5u1S5z1PtGibMgkaR-54XZmwm/n7LJrm2QMQXgG3j9XjavnYffRaRLZaSB8YqyCE4U4Z0.php(77): Drupal\Core\Template\TwigExtension->escapeFilter()
#89 /var/www/vendor/twig/twig/src/Template.php(387): __TwigTemplate_61e96a9b640aa9f1bda9458006520146->doDisplay()
#90 /var/www/vendor/twig/twig/src/Template.php(343): Twig\Template->yield()
#91 /var/www/vendor/twig/twig/src/Template.php(358): Twig\Template->display()
#92 /var/www/vendor/twig/twig/src/TemplateWrapper.php(35): Twig\Template->render()
#93 /...//core/themes/engines/twig/twig.engine(33): Twig\TemplateWrapper->render()
#94 /...//core/lib/Drupal/Core/Theme/ThemeManager.php(348): twig_render_template()
#95 /...//core/lib/Drupal/Core/Render/Renderer.php(491): Drupal\Core\Theme\ThemeManager->render()
#96 /...//core/lib/Drupal/Core/Render/Renderer.php(504): Drupal\Core\Render\Renderer->doRender()
#97 /...//core/lib/Drupal/Core/Render/Renderer.php(248): Drupal\Core\Render\Renderer->doRender()
#98 /...//core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php(238): Drupal\Core\Render\Renderer->render()
#99 /...//core/lib/Drupal/Core/Render/Renderer.php(638): Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}()
#100 /...//core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php(231): Drupal\Core\Render\Renderer->executeInRenderContext()
#101 /...//core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php(128): Drupal\Core\Render\MainContent\HtmlRenderer->prepare()
#102 /...//core/lib/Drupal/Core/EventSubscriber/MainContentViewSubscriber.php(90): Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse()
#103 [internal function]: Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray()
#104 /...//core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php(111): call_user_func()
#105 /var/www/vendor/symfony/http-kernel/HttpKernel.php(186): Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch()
#106 /var/www/vendor/symfony/http-kernel/HttpKernel.php(76): Symfony\Component\HttpKernel\HttpKernel->handleRaw()
#107 /...//core/lib/Drupal/Core/StackMiddleware/Session.php(53): Symfony\Component\HttpKernel\HttpKernel->handle()
#108 /...//core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle()
#109 /...//core/lib/Drupal/Core/StackMiddleware/ContentLength.php(28): Drupal\Core\StackMiddleware\KernelPreHandle->handle()
#110 /...//core/modules/big_pipe/src/StackMiddleware/ContentLength.php(32): Drupal\Core\StackMiddleware\ContentLength->handle()
#111 /...//core/modules/page_cache/src/StackMiddleware/PageCache.php(116): Drupal\big_pipe\StackMiddleware\ContentLength->handle()
#112 /...//core/modules/page_cache/src/StackMiddleware/PageCache.php(90): Drupal\page_cache\StackMiddleware\PageCache->pass()
#113 /...//core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\page_cache\StackMiddleware\PageCache->handle()
#114 /...//core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()
#115 /...//core/lib/Drupal/Core/StackMiddleware/AjaxPageState.php(36): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()
#116 /...//core/lib/Drupal/Core/StackMiddleware/StackedHttpKernel.php(51): Drupal\Core\StackMiddleware\AjaxPageState->handle()
#117 /...//core/lib/Drupal/Core/DrupalKernel.php(741): Drupal\Core\StackMiddleware\StackedHttpKernel->handle()
#118 /...//index.php(19): Drupal\Core\DrupalKernel->handle()
#119 {main}

@maxilein you could apply the patch from this diff:
https://git.drupalcode.org/project/charts/-/merge_requests/130.diff

Short instruction (if needed)::
First, download it to your site's root patches folder. (for example /var/www/patches/130.diff)

After that:
composer require cweagans/composer-patches

and add a patch at the bottom of the composer.json "extra" section

"extra": {
  "enable-patching": true,
    "patches": {
      "drupal/charts": {
        "Issue #3499637: Undefined array key connect_nulls": "patches/130.diff"}
    } 

Apologies for letting this warning slip in. @almador - I have updated it to use !empty() rather than ?? FALSE to ensure that the result is boolean. If tests pass, I will commit to dev.

If you want to remove the error but don't want to patch yet, just re-save your view.