GuiType.HOPPER doesn't work

[RoughlyUnderscore]

When creating a GUI with GuiType.HOPPER, the GuiItems in it won't have their actions activated (in asGuiItem)

[BlitzOffline]

So I've done some intensive testing and here's some information I got so far:

• This happens on SPIGOT but not on PAPER
• This seems to not be an issue with SPIGOT itself but rather with the library.

My test code:

• My own implementation: https://paste.helpch.at/ecihesutac.rb
• triumph-gui implementation: https://paste.helpch.at/obecukober.pl

When I get some extra time I will start looking into why this breaks if no one finds the reason before me.