Version 5.0.0 beta 9

applications/gallery/sources/Category/Category.php

@@ -624,6 +624,12 @@ class Category extends Model implements Permissions
 	 */
 	protected function _setLastComment( Comment $comment=NULL, Item $updatedItem=NULL ) : void
 	{
+		/* This can happen if we comment directly on an album. */
+		if( !( $updatedItem instanceof Image ) )
+		{
+			return;
+		}
+
 		$this->setLastImage( $updatedItem );
 	}