Basically the only gospel to mention Judas leaving at all, is John.
None of the others indicate that he left.
John though doesn't mention the passing of the emblems, and thus doesn't say whether Judas left before or after.
If we assume that John is in chronological order and Luke is not. Then Judas may have left before the passing of the emblems.
If we assume that Luke is in chronological order and John is not, then Judas definately did not leave before the passing of the emblems.
So it just comes down to how you want to twist it. One of them is wrong. Flip a coin, pick one that matches your dogma, either way your odds of being correct are the same.
Frankly if it mattered at all, you'd think god would have made sure he got bible writers who were less haphazard with their orders of events. The fact that it's not clear kind of indicates how irrelevant it is.