Handle errors when fetching actor pictures

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

lib/federation/activity_stream/converter/actor.ex

@@ -149,6 +149,8 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Actor do
          name <- name || Parser.get_filename_from_response(response_headers, url) || default_name,
          {:ok, file} <- Upload.store(%{body: body, name: name}) do
       Map.take(file, [:content_type, :name, :url, :size])
+    else
+      _ -> nil
     end
   end