Game crashes when you optimize your world

It doesn't even Optimise, all 3 ways to optimise existing world all crash with a mouse click null pointer exception.

A workaround without optimisation is to do a stand alone backup and just load the world with "I know what I am doing"...

otherwise mouse click null pointer crash.

Happens for me as well! Running Mac OS 10.14.6, with default Java settings. Occurs when optimising a world from 20w16a, haven't tested other snapshots. Really annoying as the game is super laggy due to the world format being changed, which is why I was trying to optimise my world!

This occurs with every world, not only with 20w16a.

I've tested my old world in 1.15.2 and a new world in 20w17a.

Having the same issue with a 20w16a world. Was optimizing to improve performance with the chunk format change, please fix this

According to @_LadyAgnes on Twitter, this is fixed internally and should be available/fixed in the next snapshot release.

Until then to run the world in 20w17a do a manual backup, once confirmed run the world directly and select:

• I know what I'm doing

Then your 20w16a world (or earlier▪) should load into 20w17a.

▪Please Note:

1. That the 'or earlier' is untested by myself.

2. This bug has been marked as fixed in a future version at the top of the page.