glCullFace only accepts GL_FRONT, GL_BACK and GL_FRONT_AND_BACK.
We checked if the mode was valid by performing
```
cull_mode < GL_FRONT || cull_mode > GL_FRONT_AND_BACK
```
However, this range also contains GL_LEFT and GL_RIGHT, which we would
accept when we should return a GL_INVALID_ENUM error.