Blender Git Loki

Fix bsdf_ being null; asserts for SOCK_RGBA

Use `ntreeType_Shader->idname` instead of manually entering the
ID to avoid mistakes (which I did!
`ShaderNodeTree` vs `ShaderNodetree`).

Add assert in case caller doesn't own the `nodetree_`.

Fix passing `float a, int b` to `Span` instead
of `float *, size_t size`.