Report MUC PM errors in PM tab

When you send a private message (PM) via a MUC that disallows PMs, you get an error response like this:

Error>jdev@conference.jabber.org/Ge0rG: 403 - auth: Permission denied

This response is shown in the MUC tab, however it should go into the PM tab instead.

• Changesets:
  • Revision 8495492c by mathieui on 2016-08-26T20:34:32Z:

Fix #3193 (report PM errors in PM tab)