Calling Player#closeInventory when the player does not have an open inventory will cause an InventoryCloseEvent to be fired that throws a Preconditions state check of "Title not set" when InventoryView#getTitle] is called.

Attached is a simple plugin that calls event.getPlayer().closeInventory() whenever a player sneaks, for example. Not useful at all but demonstrates the problem.

Source: https://pastebin.com/Sn4seipk

Exception: https://pastebin.com/WEZE2LzQ