It appears to have crashed while auto-saving. Would you happen to still have the previous auto-save before that?
If so, please email it to firstname.lastname@example.org. It may help us to identify what was using so much memory there.
If you don't have the save, that's ok. If it happens again, please let us know and send the previous auto save and auto save files.
In the meantime, we'll take a look through the debug.err and see what we can find.