* sip-dig.c: fixed crash on bad param
  Ignore-this: 9e73dd7095a51d15e5bc6f00e8aab98c
  
  Coverity issue.



git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@13350 d0543943-73ff-0310-b7d9-9358b9ac24b2