Don't talk to me if you don't have anything to say!
Don't bug me unless you actually have something to say!
1) Don't talk to me if you don't have anything to say!
「何も言うことがないなら話しかけてくるな!」
Don't talk to me で「話しかけてくるな」
「言うことがない」は don't have anything to say
2) Don't bug me unless you actually have something to say!
「言うことがないなら邪魔するな!」
Don't bug me で「邪魔するな」
unless で「〜でない限り・もし〜でなければ」
ご参考になれば幸いです!