Fix holes in FOF due to culling

When culling on FOFs were fixed in !1399 (merged), it unfortunately was checking the wrong bottom and top values, using the camera as the depth instead of it's own sector. The result is that it tried to cull the wrong sector, causing culled FOFs to sometimes not render if the camera was in another sector.

This patch fixes this by simply adjusting the input values to use it's own sector instead of the camera's.

Fixes #1308 (closed)