Fix a typo where an equality check should be an assignment.

(closes issue #15103)
Reported by: lmsteffan
Patches:
      transfer_crash.patch uploaded by lmsteffan (license 779)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@194477 65c4cc65-6c06-0410-ace0-fbb531ad65f3