Exception when opening a group with unusual members
Description
I have a group which has Fastpath queue's JID added as a member (test@workgroup.server). It shows in the list with red asterisk. 4.3.0 sometimes throws exception when opening this group or trying to add more such members (or say all@broadcast.server). Although it actually adds a member after all. In contrast 4.2.3 hangs in loading the page when you try to add such members or open this page, but refresh fixes the issue.
Environment
Activity
Simple reproduction recipe;
Go to a group edit page
In the "Members of this group" section, in the "Add user:" text box add a user along the lines of "test@not-my-domain.com" where not-my-domain.com is not the local XMPP domain, and not a domain that is connected via a server-to-server connection.
Click "Add"
Note; that group edit page then becomes inaccessible (with the above stack trace) until /something/ (not sure what) expires.