I am having an issue with trying to use the mouse scroll wheel in an Applied Energistics crafting terminal. Everytime I try to scroll while the mouse is in the middle of the screen the game crashes. Happens on server and single player. Happens on multiple computers.

This is from a player who plays my modpack after looking at the crash report i think its a compatibility issues with this mod and AE2

Minecraft 1.15.2
Forge 31.2.36
appliedenergistics2-7.0.1
itemscroller-forge-1.15.2-0.15.0-dev.20200412.215325
https://pastebin.com/KQT20GqL

This looks like a bug in AE2, as it's crashing in the Forge SlotItemHandler code here:
https://github.com/MinecraftForge/MinecraftForge/blob/5224533d45ad820121deb09f2419b8680f7b5f3b/src/main/java/net/minecraftforge/items/SlotItemHandler.java#L85

Meaning that they must be using the slots with a null IItemHandler reference, so any mod calling some of those methods on the slots would cause a similar crash. Maybe they didn't expect those methods to be called on the client side?

ok thank you for looking at it ill report it on there page.

Do you know if this was also an issue in 1.12.2? Or did something change in one of the mods since then so that it only now started happening?

I checked our code. I think when AE2 internally changed from IInventory over to IItemHandler, someone was a bit overzealous and also changed the base-class for ME Terminal slots from Slot to SlotItemHandler, even though we actually pass a null IInventory inventory to the Slot anyway, since slots in an ME Terminal are not backed by one.

The problem is though, getItemStackLimit (which we dont override) in SlotItemHandler does not just delegate to getSlotStackLimit (which we override) like the old vanilla Slots do. Instead it tries to query the handler (which is null).

That change was made in 2017 (1.12).

Okay it looks like I had the ME terminal slots blacklisted back in 1.12.2, but due to all the changes in the later LiteLoader and then Fabric versions, (which the 1.14.4+ Forge versions are now based on) the current 1.15.2 Forge version also has an empty blacklist by default currently. I'll need to restore the default values to that list and add it back to the config screen too.

We'll fix the bug on our end, actually. Are you doing your versions cross-version? It's possible we won't release a 1.12 bugfix, but 1.15-1.16 should receive the fix.
p.s.: Unless I am unaware of some other reason it should not work for ME terminal slots, but if your mod emulates what a player does (pick stuff up), I don't see why it should not work.
The only problem is that you're not likely to be able to "insert" this way, since the slots return 0 as their max count.

Actually, after checking it again, you might as well blacklist them, we handle the extraction in the terminal screen, so the slots are probably not worth anything to you.

AFAIK this should not affect the 1.12.2 version which is on CurseForge, ie. 0.12.0, it only affects the later versions based on the largely rewritten codebase in the LiteLoader branch and thus the versions that are based on that code base. There are 1.12.2 Forge versions with the LiteLoader branch merged back, but they are currently only on my own server, ie. not widely used. So basically don't worry about 1.12.2.

I can restore the GUI and slot blacklisting to the current Item Scroller versions. Ideally it would be nice if the slots don't cause an NPE when the normal public methods are called, but I'm not sure if you can easily do that in your case?

It's easy enough. I'll just change back to extending Vanilla Slot and it'll be fixed. But first I'll actually have to go back and check which classes are affected by this.