When the field is blank, don't warn about the field being unable to be coerced, just skip the column.
(closes http://lists.digium.com/pipermail/asterisk-dev/2009-December/041362.html)
Reported by Nic Colledge on the -dev list, fixed by me.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@236847 65c4cc65-6c06-0410-ace0-fbb531ad65f3