Fixed|Renderer: BspLeaf::MissingClusterError drawing a particle model

Particle models are drawn from the interpolated origin, which, may
lie in a degenerate BSP leaf even though the actual origin is within
the map. Consequently the BspLeaf given to R_CollectAffectingLights()
may be degenerate.
Merge branch 'master' into resourcesystem
Refactor|Resources: Completed initial C++ translation of model_t