Treat an empty FORWARD_CONTEXT the same way we treat a missing one.

(closes issue #15056)
Reported by: p_lindheimer
Patches:
      05292009_bug15056.diff uploaded by seanbright (license 71)
Tested by: p_lindheimer


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@198251 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_dial.c

@@ -503,6 +503,9 @@ static struct ast_channel *wait_for_answer(struct ast_channel *in, struct dial_l
 					tech = tmpchan;
 				} else {
 					const char *forward_context = pbx_builtin_getvar_helper(c, "FORWARD_CONTEXT");
+					if (ast_strlen_zero(forward_context)) {
+						forward_context = NULL;
+					}
 					snprintf(tmpchan, sizeof(tmpchan), "%s@%s", c->call_forward, forward_context ? forward_context : c->context);
 					stuff = tmpchan;
 					tech = "Local";