CELGenUserEvent: Fix error message from ast_json_pack

This prevents NULL from being passed into an ast_json_pack call when no
extra information is passed to the application which prevents an error
message about NULL arguments from being generated.
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Merged revisions 402755 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@402756 f38db490-d61c-443f-a65b-d21fe96a405b
pjsip_messaging, pjsip_header_funcs: Crashes due to NULL pointer dereferences

Both res_pjsip_messaging and res_pjsip_header_funcs were causing asterisk to
crash because they were trying to dereference a NULL pointer.

In the case of res_pjsip_messaging it was attempting to "print" a contact
header that did not exist.  In fact contact headers should not be part of
a SIP MESSAGE, so the offending code was simply removed.

In the case of res_pjsip_header_funcs a null private channel tech was being
passed to the function and then later dereferenced.  Added null checks (and
error logging) to the read/write function handlers to guard against crashing.

(closes issue ASTERISK-22821)
Reported by: Anthony Messina
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Merged revisions 402757 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@402758 f38db490-d61c-443f-a65b-d21fe96a405b