Issue #3012844 by bonrita, Grevil: Exception when pre-added view block is deleted

src/Form/HomeboxSettingsForm.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\homebox\Form;
 
+use Drupal\Component\Plugin\Exception\PluginNotFoundException;
 use Drupal\Core\Block\BlockManagerInterface;
 use Drupal\Core\Entity\EntityStorageInterface;
 use Drupal\Core\Theme\ThemeManagerInterface;
@@ -208,14 +209,28 @@ class HomeboxSettingsForm extends EntityForm {
     }
 
     foreach ($homebox_blocks as $block) {
-      $definition = $this->blockManager->getDefinition($block['id']);
-      $blocks[$block['region']][$block['id']] = [
-        'label' => $definition['admin_label'],
-        'entity_id' => $block['id'],
-        'entity' => NULL,
-        'category' => $definition['category'],
-        'status' => $block['status'],
-      ];
+      try {
+        $definition = $this->blockManager->getDefinition($block['id']);
+        $blocks[$block['region']][$block['id']] = [
+          'label' => $definition['admin_label'],
+          'entity_id' => $block['id'],
+          'entity' => NULL,
+          'category' => $definition['category'],
+          'status' => $block['status'],
+        ];
+      }
+      catch (PluginNotFoundException $e) {
+        $this->logger('homebox')->notice('A block does not exist anymore! Please go to the location of this message and remove it!');
+        $this->messenger()->addError('There seems to be a broken block! Please remove it or enable the module, which provides this block.');
+        $blocks[$block['region']][$block['id']] = [
+          'label' => $this->t('THIS BLOCK IS BROKEN! PLEASE REMOVE IT!.'),
+          'entity_id' => $block['id'],
+          'entity' => NULL,
+          'category' => $this->t('Broken'),
+          'status' => $block['status'],
+        ];
+      }
+
       if (isset($block['weight'])) {
         $blocks[$block['region']][$block['id']]['weight'] = $block['weight'];
       }
@@ -478,8 +493,7 @@ class HomeboxSettingsForm extends EntityForm {
           ['query' => ['block-enable' => $block_id]]
         ),
       ];
-    }
-    else {
+    } else {
       $operations['disable'] = [
         'title' => t('Disable'),
         'weight' => 40,
@@ -543,5 +557,4 @@ class HomeboxSettingsForm extends EntityForm {
     }
     return $this->theme;
   }
-
 }