Uncaught PHP Exception: MissingValueContextException After upgrading to version 8.8.5, I can't access the main web page, but I can log in to the admin panel. When I turn on the verbose logging funcionality I receive the following error message:

Drupal\Component\Plugin\Exception\MissingValueContextException: Required contexts without a value: view_mode in Drupal\Core\Plugin\Context\ContextHandler-&gt;applyContextMapping() (line 155 of core/lib/Drupal/Core/Plugin/Context/ContextHandler.php).

Drupal\panels\Plugin\DisplayBuilder\StandardDisplayBuilder-&gt;buildRegions() (Line: 183)
Drupal\panels\Plugin\DisplayBuilder\StandardDisplayBuilder-&gt;build() (Line: 338)
Drupal\panels\Plugin\DisplayVariant\PanelsDisplayVariant-&gt;build() (Line: 29) 
Drupal\page_manager\Entity\PageVariantViewBuilder-&gt;view() (Line: 105) 
Drupal\Core\Entity\Controller\EntityViewController-&gt;view() call_user_func_array() (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber-&gt;Drupal\Core\EventSubscriber\{closure}() (Line: 573)
Drupal\Core\Render\Renderer-&gt;executeInRenderContext() (Line: 124) Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber-&gt;wrapControllerExecutionInRenderContext() (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber-&gt;Drupal\Core\EventSubscriber\{closure}() (Line: 151)
Symfony\Component\HttpKernel\HttpKernel-&gt;handleRaw() (Line: 68) 
Symfony\Component\HttpKernel\HttpKernel-&gt;handle() (Line: 57)
Drupal\Core\StackMiddleware\Session-&gt;handle() (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle-&gt;handle() (Line: 191)
Drupal\page_cache\StackMiddleware\PageCache-&gt;fetch() (Line: 128)
Drupal\page_cache\StackMiddleware\PageCache-&gt;lookup() (Line: 82)
Drupal\page_cache\StackMiddleware\PageCache-&gt;handle() (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware-&gt;handle() (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware-&gt;handle() (Line: 23)
Stack\StackedHttpKernel-&gt;handle() (Line: 708)
Drupal\Core\DrupalKernel-&gt;handle() (Line: 19)


I don't know if this is a core or a module error, any help appreciated.

Actual system: Drupal 8.8.5, PHP 7.4.5, 5.5.5-10.1.44-MariaDB-0+deb9u1

Thanks.
It seems to be related to a new constraint added on releases, as seen on https://www.drupal.org/project/drupal/issues/3113474
As &quot;view mode&quot; is asked, with no default context, some modules like Panels IPE, Panels, MiniLayout may generate problems if you ask to display a single entity field as FieldBlock.
Just apply patch on https://www.drupal.org/files/issues/2020-02-13/3001313--63_0.patch ; for the record :

--- a/core/modules/layout_builder/src/Plugin/Derivative/FieldBlockDeriver.php
+++ b/core/modules/layout_builder/src/Plugin/Derivative/FieldBlockDeriver.php
@@ -124,7 +124,14 @@ public function getDerivativeDefinitions($base_plugin_definition) {
           $context_definition->addConstraint('Bundle', [$bundle]);
           $derivative['context_definitions'] = [
             'entity' => $context_definition,
-            'view_mode' => new ContextDefinition('string'),
+            'view_mode' =>  new ContextDefinition(
+              'string',
+              $this->t('View Mode'),
+              FALSE,
+              FALSE,
+              NULL,
+              'default'
+            ),
           ];