https://pastebin.com/6rBBGCyV

You clicked on an item that has a null in it's tag, normally this is not posible. One of your mods puts a null into the item tag.
This is an issue with one of your other mods.

@tom5454 shouldn't your mod ignore null tags?
this issue should be tagged "enhancement" to prevent future crashes

The null tag is deeply within the item tag. Attempting to write this item with vanilla code will crash.