Prevent a crash on outbound SIP MESSAGE requests.

If a From header on an outbound out-of-call SIP MESSAGE were
malformed, the result could crash Asterisk.

In addition, if a From header on an incoming out-of-call SIP
MESSAGE request were malformed, the message was happily accepted
rather than being rejected up front. The incoming message path
would not result in a crash, but the behavior was bad nonetheless.

(closes issue ASTERISK-22185)
reported by Zhang Lei


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@397254 f38db490-d61c-443f-a65b-d21fe96a405b