ISTWCMS-5206: fixing error when there is no image on the entity pre save

uw_cfg_common.module

@@ -113,30 +113,34 @@ function uw_cfg_common_entity_presave(EntityInterface $entity) {
       // Get the value of the image field.
       $image = $entity->field_uw_hero_image->getValue();
 
-      // Load the file from the hero image.
-      $file = \Drupal::entityTypeManager()
-        ->getStorage('file')
-        ->load($image[0]['target_id']);
-
-      // Load the image styles that are needed for the hero.
-      $uw_styles = \Drupal::service('uw_cfg_common.uw_service')->uwGetResponsiveImageStyles();
-
-      // Step through each of the image styles and ensure that
-      // the derivative is created.
-      foreach ($uw_styles as $uw_style) {
-
-        // Load the image style.
-        $style = \Drupal::entityTypeManager()
-          ->getStorage('image_style')
-          ->load($uw_style);
-
-        // Get the styled image derivative.
-        $destination = $style->buildUri($file->getFileUri());
-
-        // If the derivative doesn't exist yet (as the image style may have been
-        // added post launch), create it.
-        if (!file_exists($destination)) {
-          $style->createDerivative($file->getFileUri(), $destination);
+      // Ensure that there actually is an image to process.
+      if ($image) {
+
+        // Load the file from the hero image.
+        $file = \Drupal::entityTypeManager()
+          ->getStorage('file')
+          ->load($image[0]['target_id']);
+
+        // Load the image styles that are needed for the hero.
+        $uw_styles = \Drupal::service('uw_cfg_common.uw_service')->uwGetResponsiveImageStyles();
+
+        // Step through each of the image styles and ensure that
+        // the derivative is created.
+        foreach ($uw_styles as $uw_style) {
+
+          // Load the image style.
+          $style = \Drupal::entityTypeManager()
+            ->getStorage('image_style')
+            ->load($uw_style);
+
+          // Get the styled image derivative.
+          $destination = $style->buildUri($file->getFileUri());
+
+          // If the derivative doesn't exist yet (as the image style may have been
+          // added post launch), create it.
+          if (!file_exists($destination)) {
+            $style->createDerivative($file->getFileUri(), $destination);
+          }
         }
       }
     }