need null checking when calling C API

[blend2d]

need null checking when calling C API

[kobalicek]

The object must be initialized otherwise it's undefined what would happen. It's very similar to passing null FILE* pointer to fwrite(), for example, etc... Blend2D instances must be initialized by Init() before use and destroyed by Reset() after they go out of scope. C++ API does it by design, C API doesn't.

If you pass a null pointer to C API or some object's impl is null it means that the passed instance was not properly initialized as Blend2D never uses nulls for impls (instead a built-in none instance is used, which is still valid impl).

[Wiladams]

Yah, I figured as much. The 'C' interface is essentially "no guard rails", which is fine as for my own LuaJIT wrapper, I'm doing what the C++ interface does (init, reset). It might just be worthwhile documenting the fact that the C interface is more "raw". I know it's already documented that you SHOULD do the Init/Reset thing, but maybe more explicit?

This wasn't actually a problem for me, I ran into by accident.

So far so good overall.