Fix app_disa to set the proper variable before goign to invalid (bug #5439)

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@6845 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_disa.c

@@ -338,6 +338,7 @@ static int disa_exec(struct ast_channel *chan, void *data)
 		int recheck = 0;
 
 		if (!ast_exists_extension(chan, ourcontext, exten, 1, chan->cid.cid_num)) {
+			pbx_builtin_setvar_helper(chan, "INVALID_EXTEN", exten);
 			exten[0] = 'i';
 			exten[1] = '\0';
 			recheck = 1;