Pressing hotbar keys in spectator mode crashes the game.

In spectator mode, pressing keys that correspond to the hotbar slots crashes the game.

Steps to reproduce:

1. Open any world.
2. Go into spectator mode.
3. Press a key that corresponds to a hotbar slot.
4. Observe that the game crashed.

The number keys, if not bound to a hotbar slot, do not cause the crash.

Keys rebound to the hotbar slots, however, do cause the crash.

The offhand key does not seem to crash the game.