Bug/Issue Mysterious "Fatal Error"

I was playing around, checking out some sniper rifles with /spawnitem commonsniperrifle and as I went to delete one of the rifles, this happened. (See attached screenshot) It then immediately stopped responding, and I had to quit it.

It happened a couple minutes earlier when I tried to open the food section of my inventory, and the same error box appeared, but I just thought that was how this game crashed, so I didn't get a screenshot. However, the walls of text appear to have been the same from what I remember.

In any case, I'd like to know what it means, should it continue.

Thanks for the help!