Shadow errors with point lights

[typewriter1]

I will attempt to fix this - a PR to fix would be accepted.

The exact error is this:
:display:gsg:glgsg(error): Sampler type of GLSL shader input p3d_LightSource[4].shadowMap does not match type of texture dummy-shadow-cube.
It occurs every frame, for every lights, even non point lights. If no enabled point lights are in the scene, the error does not occur.