Got this crash report when exploring the Nether:
https://gist.github.com/whichonespink44/f1cb94ba93a84ee4fbe22a1d03f81c4e

Log file:
fml-client-latest.zip

Fyi... I was able to log back into my world after the crash and haven't experienced it again.

This should have been fixed at the latest in 1.2.2, please update :)

As unlikely as I hope it to be, if it happens a again with that version, please reopen with new log, thanks!