Surfaces that will never be used for drawing still get added in RB_RenderDrawSurfaces()

[VReaperV]

See https://users.unvanquished.net/~sweet/reaper/map-example_1.dpk for an example.

The sky and portal surfaces are skipped in R_CreateWorldVBO(), but RB_RenderDrawSurfaces() still adds the sky surfaces, which it ends up uselessly copying into tess.verts and tess.indexes and, in this case, overflowing SHADER_MAX_VERTEXES. Those surfaces are never used for drawing.