Fix a silly infinite loop when choosing an invalid option.

(closes issue #12315)
Reported by: jmls


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@112068 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_voicemail.c

@@ -6130,6 +6130,7 @@ static int vm_options(struct ast_channel *chan, struct ast_vm_user *vmu, struct
 			cmd = 't';
 			break;
 		default: 
+			cmd = 0;
 			snprintf(prefile, sizeof(prefile), "%s%s/%s/temp", VM_SPOOL_DIR, vmu->context, vms->username);
 			if (ast_fileexists(prefile, NULL, NULL))
 				cmd = ast_play_and_wait(chan, "vm-tmpexists");