Description of the issue:

I added items into engie workbench, and tried the duplication glitch, after taking weapon it looked like this

and i tried to add something into those slots and it crashed.

Crashlog:

crash-2020-06-23_19.43.52-client.txt

Versions & Modlist

forge 31.2.9 , IE [1.15.2] [0.15-105 #10] and basic, not modified modlist of the server

Duplicate of #4028 in its cause, should be resolved by the same fix.