my game crashes when a pig is "eating" and grass "grows" from an byg overgrown stone grass block. I don't know if this happens with other animals too.

Going to retest this this weekend. I think it is fixed in the lastest version but I didn't test for this error in the last release.
It would grow when a player used bonemeal but only flowers. It was actually crashing if a player does it too but the crash exception is caught for players.

Okay I've confirmed this issue is fixed in the last release. Thanks for your bug report!

This was fixed but had not closed it. So I reconfirmed it is still fixed.

Confirming this is fixed. Ran a 24 hour test with pigs on a mixture of grass and overgrown blocks from BYG. Grassblocks grew, overgrown blocks got some flowers. No crashes.

Thanks for your issue report.