Fix online address validation

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/federation/activity_pub/transmogrifier.ex

@@ -95,6 +95,8 @@ defmodule Mobilizon.Federation.ActivityPub.Transmogrifier do
       {:ok, activity, event}
     else
       {:existing_event, %Event{} = event} -> {:ok, nil, event}
+      {:error, _, _} -> :error
+      {:error, _} -> :error
     end
   end
 

lib/federation/activity_stream/converter/event.ex

@@ -226,7 +226,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Event do
   defp date_to_string(%DateTime{} = date), do: DateTime.to_iso8601(date)
 
   defp get_online_address(attachments) do
-    Enum.find_value(attachments, [], fn attachment ->
+    Enum.find_value(attachments, fn attachment ->
       case attachment do
         %{
           "type" => "Link",