Don't try to dereference the dbfile pointer if

we know that it's NULL.

(closes issue #13092)
Reported by: gknispel_proformatique
Patches:
      trunk_sqlite_check_vars_null.patch uploaded by gknispel (license 261)



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@131361 65c4cc65-6c06-0410-ace0-fbb531ad65f3