Second computer screen blank on OSX

[eldahl]

Describe the bug
The computer to the left appears with a black screen. Keyboard input is not visible as on windows build.

To Reproduce
Build and run on OSX. Observe the left computer.

[Meisaka]

The computer on the left is entity 101, and is technically the first of the two.
Debugging this a bit, one of the glDrawElements calls in RenderSystem::BeginPointLightPass() raises an illegal operation error,
a glGetError() check doesn't happen until the beginning of the texture's Load() method.
The texture Load method wrongly bails out early after reading the failed render pass' error code.
See render-system.cpp for the offending line