Returned None

IDK why, comment, must be really important though.

client/ayon_core/plugins/publish/extract_thumbnail.py

@@ -755,6 +755,6 @@ class ExtractThumbnail(pyblish.api.InstancePlugin):
                     host_name, product_type, product_name, task_name, task_type
                 )
             )
-            return
+            return None
 
         return ThumbnailDef.from_dict(profile)