Light clusters corruption: light indices beyond currently active lights

[w23]

minidemo_08_... gets point light index = 7 from clusters, but there are only 7 lights (index 6 being max). This manifests as NaNs in point light calculation because out-of-bounds values don't make sense.

Not sure if investigating and fixing this makes sense, as we're eventually plan to go away from clusters. Close this issues when/if we do.