Update to alpha3/4 breaks (WSOD) Field Block configuration screens

fieldblock family,

I updated fieldblock from 2.0-alpha1 to 2.0-alpha3 and encountered a white screen of death when attempting to access Field As Block block configuration pages (I confirmed this issue is also present when using fieldblock version 2.0-alpha4). We are running Drupal Core 8.5.3. The PHP error written to my DB Log is as follows:

Error: Call to undefined method Drupal\Core\Form\FormState::getCompleteFormState() in Drupal\fieldblock\Plugin\Block\FieldBlock->blockForm() (line 240 of /srv/sandyspringbank.com/www/web/modules/contrib/fieldblock/src/Plugin/Block/FieldBlock.php) #0 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Block/BlockBase.php(182): Drupal\fieldblock\Plugin\Block\FieldBlock->blockForm(Array, Object(Drupal\Core\Form\FormState)) #1 /srv/sandyspringbank.com/www/web/core/modules/block/src/BlockForm.php(141): Drupal\Core\Block\BlockBase->buildConfigurationForm(Array, Object(Drupal\Core\Form\SubformState)) #2 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Entity/EntityForm.php(117): Drupal\block\BlockForm->form(Array, Object(Drupal\Core\Form\FormState)) #3 [internal function]: Drupal\Core\Entity\EntityForm->buildForm(Array, Object(Drupal\Core\Form\FormState)) #4 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Form/FormBuilder.php(514): call_user_func_array(Array, Array) #5 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Form/FormBuilder.php(271): Drupal\Core\Form\FormBuilder->retrieveForm('block_form', Object(Drupal\Core\Form\FormState)) #6 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Controller/FormController.php(74): Drupal\Core\Form\FormBuilder->buildForm('block_form', Object(Drupal\Core\Form\FormState)) #7 [internal function]: Drupal\Core\Controller\FormController->getContentResult(Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\RouteMatch)) #8 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array) #9 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Render/Renderer.php(582): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() #10 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure)) #11 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) #12 /srv/sandyspringbank.com/www/vendor/symfony/http-kernel/HttpKernel.php(151): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() #13 /srv/sandyspringbank.com/www/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1) #14 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #15 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #16 /srv/sandyspringbank.com/www/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(99): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #17 /srv/sandyspringbank.com/www/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(78): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true) #18 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #19 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(50): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #20 /srv/sandyspringbank.com/www/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #21 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/DrupalKernel.php(664): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #22 /srv/sandyspringbank.com/www/web/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request)) #23 {main}.
Error: Call to undefined method Drupal\Core\Form\FormState::getCompleteFormState() in Drupal\fieldblock\Plugin\Block\FieldBlock->blockForm() (line 240 of /srv/sandyspringbank.com/www/web/modules/contrib/fieldblock/src/Plugin/Block/FieldBlock.php) #0 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Block/BlockBase.php(182): Drupal\fieldblock\Plugin\Block\FieldBlock->blockForm(Array, Object(Drupal\Core\Form\FormState)) #1 /srv/sandyspringbank.com/www/web/core/modules/block/src/BlockForm.php(141): Drupal\Core\Block\BlockBase->buildConfigurationForm(Array, Object(Drupal\Core\Form\SubformState)) #2 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Entity/EntityForm.php(117): Drupal\block\BlockForm->form(Array, Object(Drupal\Core\Form\FormState)) #3 [internal function]: Drupal\Core\Entity\EntityForm->buildForm(Array, Object(Drupal\Core\Form\FormState)) #4 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Form/FormBuilder.php(514): call_user_func_array(Array, Array) #5 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Form/FormBuilder.php(271): Drupal\Core\Form\FormBuilder->retrieveForm('block_form', Object(Drupal\Core\Form\FormState)) #6 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Controller/FormController.php(74): Drupal\Core\Form\FormBuilder->buildForm('block_form', Object(Drupal\Core\Form\FormState)) #7 [internal function]: Drupal\Core\Controller\FormController->getContentResult(Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\RouteMatch)) #8 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array) #9 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/Render/Renderer.php(582): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() #10 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure)) #11 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) #12 /srv/sandyspringbank.com/www/vendor/symfony/http-kernel/HttpKernel.php(151): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() #13 /srv/sandyspringbank.com/www/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1) #14 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #15 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #16 /srv/sandyspringbank.com/www/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(99): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #17 /srv/sandyspringbank.com/www/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(78): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true) #18 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #19 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(50): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #20 /srv/sandyspringbank.com/www/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #21 /srv/sandyspringbank.com/www/web/core/lib/Drupal/Core/DrupalKernel.php(664): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #22 /srv/sandyspringbank.com/www/web/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request)) #23 {main}.

We are working to generate a patch to resolve this issue.