Require related object for notifications to filter on content

lib/pleroma/notification.ex

@@ -178,6 +178,7 @@ defmodule Pleroma.Notification do
         from([_n, a, o] in query,
           where:
             fragment("not(?->>'content' ~* ?)", o.data, ^regex) or
+              fragment("?->>'content' is null", o.data) or
               fragment("?->>'actor' = ?", o.data, ^user.ap_id)
         )
     end