https://imgur.com/TTzcZoe

it crashed when I try to upgrade/delete miniloader.

It only happens when loader is doing something (holding materials on belt itself)

If I remove all materials from miniloader, crash doesnt happen.

I guess this bug is related with the factor that 'trying to change miniloader entity when it holds something'

What method were you using to remove the miniloader? This error indicates that a robot mined the miniloader, but the robot didn't have an inventory to store the items on the belt. Were you using a construction or deconstruction mod like Nanobots?

I've added code that detects this situation and it shouldn't crash anymore, but the items on the belt will be lost.

Yes I used nanobot and construction robots. Thanks for your update! it never crashed agian :)