Change NULL pointer check to be ast_strlen_zero.

The 'digit' variable is guaranteed to be non-NULL, so the if
statement could never evaluate true. Changing to ast_strlen_zero
makes the logic correct.

This was found while reviewing ast_channel_ao2 code review.



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@184078 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_senddtmf.c

@@ -104,7 +104,7 @@ static int manager_play_dtmf(struct mansession *s, const struct message *m)
 		astman_send_error(s, m, "Channel not specified");
 		return 0;
 	}
-	if (!digit) {
+	if (ast_strlen_zero(digit)) {
 		astman_send_error(s, m, "No digit specified");
 		ast_mutex_unlock(&chan->lock);
 		return 0;