Avoid 404 on the notifications because of the parameters in the URL

At the moment the parameters since_id can be a hash rather an integer so the requests created some 404 errors.

The code was already modified in the original mastodon code.

This is a patch to resolve the bugs:

diff --git a/app/javascript/mastodon/actions/notifications.js b/app/javascript/mastodon/actions/notifications.js
index ad6430b82..23569c11d 100644
--- a/app/javascript/mastodon/actions/notifications.js
+++ b/app/javascript/mastodon/actions/notifications.js
@@ -105,7 +105,7 @@ export function expandNotifications({ maxId } = {}, done = noOp) {
     };
 
     if (!maxId && notifications.get('items').size > 0) {
-      params.since_id = notifications.getIn(['items', 0]);
+      params.since_id = notifications.getIn(['items', 0, 'id']);
     }