It hasn't happened again, so yes a one time only thing.
If it ever happens again I'll try to male a note of the steps before the crash.

Hi,

First of great game! But too bad it crashed today. I attached the last autosave and the log file, apparently it crashed at indexing part of the transport belt (or so it seems from the names in the log file).
The only mod that was active at the moment was Angels Warehouses.
Hope you can use this ...