Issue #3327442 by mably: handle case where ImageStyle has been overriden by other modules

Closes #3327442

src/Entity/ImageAPIOptimizePipeline.php

@@ -149,8 +149,10 @@ class ImageAPIOptimizePipeline extends ConfigEntityBase implements ImageAPIOptim
     $style_storage = $this->entityTypeManager()->getStorage('image_style');
     foreach ($style_storage->loadMultiple() as $style) {
       /** @var ImageStyleWithPipeline $style */
-      if ($style->hasPipeline() && $style->getPipelineEntity()->id() == $this->id()) {
-        $style->flush();
+      if ($style instanceof  ImageStyleWithPipeline) {
+        if ($style->hasPipeline() && $style->getPipelineEntity()->id() == $this->id()) {
+          $style->flush();
+        }
       }
     }