[MCL-5698] opening snaphot versions f mc show error of launcher on launching

What I expected to happen was...:
start snapshot 17w06a

What actually happened was...:
snapshot start, but show error if I click on play (image on this report)

Steps to Reproduce:
I don't know, any edit of source code

Attachments

So... you edited the source code and this happened?

no, I think that can help, because I can't edit source code of games

You should look up what "reproduce" means.

We need to see your launchers output logs. Please follow the instructions on this page: https://imgur.com/a/N7sQD