handle empty last_fetch

lib/pleroma/object/fetcher.ex

@@ -211,14 +211,14 @@ defp log_fetch_error(id, error) do
   end
 
   # if its already an activity, dont wrap
-  defp prepare_activity_params(%{"object" => _ } = data), do: data
+  defp prepare_activity_params(%{"object" => _} = data), do: data
 
   defp prepare_activity_params(data) do
     %{
       "type" => "Create",
       # Should we seriously keep this attributedTo thing?
       "actor" => data["actor"] || data["attributedTo"],
-      "object" => data,
+      "object" => data
     }
     |> Maps.put_if_present("to", data["to"])
     |> Maps.put_if_present("cc", data["cc"])

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -1862,7 +1862,14 @@ def enqueue_outbox_fetches(
         %{outbox: outbox_address, last_outbox_fetch: last_fetch, local: false} = user
       ) do
     with(
-      last_fetch <- last_fetch.to_unix(),
+      last_fetch <-
+        if last_fetch == nil do
+          0
+        else
+          last_fetch
+          |> DateTime.from_iso8601()
+          |> DateTime.to_unix()
+        end,
       now <- DateTime.utc_now().to_unix(),
       # future => epoch stuff, let it pass
       # >60 secs in past => ok