[C] Open hopper inventories even if they are not associated to a tile entity. Fixes BUKKIT-4722

**Issue:**
Trying to open an inventory of type InventoryType.HOPPER that has been created using the servers createInventory-method does not work.

**Justification:**
It should be possible to open custom created hopper inventories like any other inventory.

**JIRA Ticket:**
https://bukkit.atlassian.net/browse/BUKKIT-4722