Fix cloaking an item as itself

[Gronglegrowth]

Added a check to both item and block model cloaking to ensure they only actually run if the models are different. Before this change, trying to do this would crash with a stack overflow error,,,

[DaFuqs]

While that solves this one problem, it kind of feels like a bandaid fix for one out of more issues. It still messes up when you cloak two items as one another or a->b->c

A fix that solves all issues, instead of just this single instance would make more sense.

[Gronglegrowth]

I hadn't known there were more issues; I was only aware of this one. Something more comprehensive then would indeed be better.