FIX: Correct off-by-one error in __ipairs iterator which breaks under 52COMPAT

I recently was informed Rubic0n has compatibility issues with Inventory Extender.

This only happens due to having 52COMPAT enabled on those builds. Without 52COMPAT, the actual ipairs iterator is never called and it simply falls back to pairs, which works on its own. This corrects the off-by-one, although, I'd mention the ipairs iterator ordinarily is simply dead code, so maybe we could get rid of it. Or not.