Make sure it's a Contacts before accessing fields

pyrogram/client/client.py

@@ -2412,6 +2412,8 @@ class Client:
                 time.sleep(e.x)
                 continue
             else:
+                if isinstance(contacts, types.contacts.Contacts):
                     log.info("Contacts count: {}".format(len(contacts.users)))
                     self.fetch_peers(contacts.users)
+
                 return contacts