I'm not positive this is the best way about it... As @frymaster said - Any plugin that currently exists that may be passing an invalid type is now broken if this gets pulled. 

> it won't even be called unless another inventory type is added without being added to the switch.

This is my other concern - Some were missed which were added by this PR. I would keep it as `0` rather than `-1` or and exception. This allows for something to be displayed rather than just spitting out errors.

I'll consult a core member about this however.