Kick due to error when in crafting menu

[Alvin-HZ]

I've searched existing issues and couldn't find a duplicate.

• I confirm this is not a duplicate.

Operating System

Arch Linux

Server Software Version/Commit

987aaad

What happened?

When in crafting menu, if you select an item then click anywhere that is not a slot, you will be kicked for Error while reading incoming packet Invalid slot

To Reproduce

1. Get any item from creative or /give
2. Open crafting menu from /craft
3. Select an item with your cursor
4. Click anywhere that is not a slot or outside the gui with the item

Expected behavior

No kick