No feedback when address format contains unescaped characters

[singpolyma]

Describe the bug

When adding an XMPP JabberID that contains characters that bifrost requires to be escaped, sent messages just silently fail.

To Reproduce

1. Open direct message with @xmpp_+1<tel>=40cheogram.com:matrix.org where is any US or Canada phone number
2. Send a message
3. Observe that you receive no SMS at that number and no error in your Matrix client
4. Open direct message with @_xmpp_=2b1<tel>=40cheogram.com:matrix.org
5. Send a message
6. Observe that you do receive SMS at that number

Expected behavior

An error should be returned indicating to the user that they probably need to escape something, or at very least that their message has not been delivered.

[singpolyma]

On re-reading, I obviously missed the leading underscore in my attempt with the + -- when I add the underscore I do get an error trying to open that DM. Bleh, my bad.