Python API - Seg fault when using Config.isColorSpaceLinear() with invalid color space name

```
>>> import PyOpenColorIO as ocio
>>> cfg = ocio.Config.CreateFromBuiltinConfig('studio-config-v1.0.0_aces-v1.3_ocio-v2.1')
>>> cfg.isColorSpaceLinear('asdf', ocio.REFERENCE_SPACE_SCENE)
Segmentation fault
```
😮 