InvalidArgumentException: "0" is an invalid render array key

Problem/Motivation

We're running Drupal Core 10.3.2 with Layout Paragraphs v2.0.8, but have also tested v2.1.x and in either case, an upgrade to Drupal Core from version 10.2.7 to 10.3.2 causes a fatal twig rendering error when editing a component using Layout Paragraphs.

Error output:
InvalidArgumentException: "0" is an invalid render array key. Value should be an array but got a string. in Drupal\Core\Render\Element::children() (line 97 of core/lib/Drupal/Core/Render/Element.php).

Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 248)
Drupal\Core\Render\Renderer->render(Array) (Line: 475)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 41)
__TwigTemplate_8b57d7c878637527bb7b8aede6b1f39b->doDisplay(Array, Array) (Line: 360)
Twig\Template->yield(Array) (Line: 335)
Twig\Template->render(Array) (Line: 38)
Twig\TemplateWrapper->render(Array) (Line: 33)
twig_render_template('themes/custom/hg_mercury_dxe/templates/form/input--submit--button.html.twig', Array) (Line: 348)
Drupal\Core\Theme\ThemeManager->render('input__submit', Array) (Line: 547)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 504)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 248)
Drupal\Core\Render\Renderer->render(Array) (Line: 577)
Drupal\Core\Template\TwigExtension->renderVar(Array) (Line: 48)
__TwigTemplate_abd4ac79dff48adf5cf3ea130e30611a->doDisplay(Array, Array) (Line: 360)
Twig\Template->yield(Array) (Line: 335)
Twig\Template->render(Array) (Line: 38)
Twig\TemplateWrapper->render(Array) (Line: 33)
twig_render_template('modules/contrib/paragraphs/templates/paragraphs-actions.html.twig', Array) (Line: 348)
Drupal\Core\Theme\ThemeManager->render('paragraphs_actions', Array) (Line: 491)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 504)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 248)
Drupal\Core\Render\Renderer->render(Array) (Line: 475)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 115)
__TwigTemplate_5b1e40da0c929e5c9dfdb896587417a9->doDisplay(Array, Array) (Line: 360)
Twig\Template->yield(Array) (Line: 335)
Twig\Template->render(Array) (Line: 38)
Twig\TemplateWrapper->render(Array) (Line: 33)
twig_render_template('core/modules/system/templates/table.html.twig', Array) (Line: 348)
Drupal\Core\Theme\ThemeManager->render('table', Array) (Line: 491)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 248)
Drupal\Core\Render\Renderer->render(Array) (Line: 475)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 51)
__TwigTemplate_5b79baeac8d1b54d403e8c7542b176b3->doDisplay(Array, Array) (Line: 360)
Twig\Template->yield(Array) (Line: 335)
Twig\Template->render(Array) (Line: 38)
Twig\TemplateWrapper->render(Array) (Line: 33)
twig_render_template('core/modules/system/templates/field-multiple-value-form.html.twig', Array) (Line: 348)
Drupal\Core\Theme\ThemeManager->render('field_multiple_value_form', Array) (Line: 491)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 504)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 504)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 248)
Drupal\Core\Render\Renderer->render(Array, ) (Line: 238)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 638)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 239)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 128)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object)
call_user_func(Array, Object, 'kernel.view', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch(Object, 'kernel.view') (Line: 186)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 53)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object, 1, 1) (Line: 741)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Steps to reproduce

1. Upgrade Drupal to 10.3.2
2. Upgrade Layout Paragraphs v2.0.8 and edit an existing Layout paragraphs component prior to upgrading Drupal Core to v10.3.2

It appears that any component that is created after the Drupal Core upgrade is unaffected. Any component created prior to the upgrade and that is then edited renders the error.

This is related to the following issue reported for Drupal Core:
https://www.drupal.org/project/drupal/issues/3470907 🐛 InvalidArgumentException: "0" is an invalid render array key Postponed: needs info