When you accidentally index a property with a Handle of the wrong kind, this gives no error indication at compile time. I think `VertexProperty[EdgeHandle]` etc. should not compile. `PropertyPtr::operator[]` currently has overloads for `OpenVolumeMeshHandle` and `size_t` arguments, IMO there should be only one function that takes the correct specific handle type. The `size_t` overload is dangerous in combination with the Handle's implicit `int()` conversion, as it would still allow this kind of type unsafety, I think we should at least not keep both, if not even remove both. This would be a backwards-incompatible change - maybe best to handle with depreciation macros?