Vanilla GUI anti dupe fixes.

[Dovias]

These not really are snippets but, these are useful things which prevent some annoying bugs, or dupes within vanilla GUI's

• Anti "Move all items from container to player's cursor" dupe
  Requires skript-mirror:

import:
  org.bukkit.event.inventory.InventoryType
  org.bukkit.event.inventory.InventoryAction

on inventory click:
  if event.getWhoClicked().getOpenInventory().getTopInventory().getType() is InventoryType.CHEST: #You can change type to your's gui Type.
    if event.getWhoClicked().getOpenInventory().getTopInventory().getTitle() is "Name of chest":
      if event.getAction() is InventoryAction.COLLECT_TO_CURSOR:
        if "%event.getWhoClicked().getOpenInventory().getTopInventory().getContents()%" contains         "%event.getCursor().asOne()%":
          cancel event

• Anti "lock item in slot that contains air" whenever inventory click event is cancelled
  Requires skript-mirror:

import:
  org.bukkit.event.inventory.InventoryDragEvent

on InventoryDragEvent:
  if event-inventory's name is "Title name of inventory":
    cancel event