transmogrifier: when determining followers collection URI, we may need to fetch the actor

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -158,7 +158,7 @@ def fix_implicit_addressing(%{"to" => to, "cc" => cc} = object, followers_collec
   def fix_implicit_addressing(object, _), do: object
 
   def fix_addressing(object) do
-    %User{} = user = User.get_cached_by_ap_id(object["actor"])
+    %User{} = user = User.get_or_fetch_by_ap_id(object["actor"])
     followers_collection = User.ap_followers(user)
 
     object