ISTWCMS-7275: Fix minor syntax consistency in error message rendering.

A trailing comma was added to ensure consistent syntax formatting across multiple block plugins. This change does not impact functionality but improves code readability and adherence to coding standards.

src/Plugin/Block/ReferenceAuthorsBlock.php

@@ -101,7 +101,7 @@ class ReferenceAuthorsBlock extends BlockBase implements ContainerFactoryPluginI
     // before using view, to prevent call function on null errors.
     if (!$view) {
       return [
-        '#markup' => $this->t('There was an error loading the block.')
+        '#markup' => $this->t('There was an error loading the block.'),
       ];
     }
 

src/Plugin/Block/ReferenceBlock.php

@@ -101,7 +101,7 @@ class ReferenceBlock extends BlockBase implements ContainerFactoryPluginInterfac
     // before using view, to prevent call function on null errors.
     if (!$view) {
       return [
-        '#markup' => $this->t('There was an error loading the block.')
+        '#markup' => $this->t('There was an error loading the block.'),
       ];
     }
 

src/Plugin/Block/ReferenceKeywordsBlock.php

@@ -101,7 +101,7 @@ class ReferenceKeywordsBlock extends BlockBase implements ContainerFactoryPlugin
     // before using view, to prevent call function on null errors.
     if (!$view) {
       return [
-        '#markup' => $this->t('There was an error loading the block.')
+        '#markup' => $this->t('There was an error loading the block.'),
       ];
     }