[BUG] When Leave/unbond , MsgDeposit don't need to include coin

At the moment, if we don't include coin , it pass the validation , but it throw an error later. {"level":"info","coins":[{"asset":"THOR.RUNE","amount":"0"}],"from":"tthor10vzsst8sa2lkjnaj5f089z6mcf4lt3usd0qyqr","memo":"LEAVE:tthor13sf9ts8fu44lk2jxuaptfdxxt6myv6l957zepz","time":"2021-02-17T06:18:28Z","message":"receive MsgDeposit"} {"level":"error","error":"0rune: invalid coins","time":"2021-02-17T06:18:28Z","message":"fail to process MsgDeposit"}