Delete the source only when it was found

tubesync/sync/tasks.py

@@ -792,6 +792,7 @@ def delete_all_media_for_source(source_id, source_name, source_directory):
         (source and source.delete_removed_media) or
         (directory_path / '.to_be_removed').is_file()
     )
+    if source:
         with atomic(durable=True):
             source.delete()
     if remove: