First, if the light data is not marked as correct, we should not be
parsing it in the first place. This will eliminate errors from
parsing possibly different versioned light data.
Secondly, if parsing the light data throws an exception (from
the SWMRNibbleArray constructor), then we can simply mark
the returned chunk as having incorrect light data - rather than
propagating the exception and causing the chunk to be re-generated.
This is based on Moonrise's 1.21.2 branch, but this on
1.21.1 so some diffs cannot be applied (and this doesn't
compile).
See moonrise_update_1_21_2.txt for progress
