Fix strange behaviour in O2-N2 continuum
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The O2-N2 continuum is producing spuriously strong absorption at the red-end of its range. This is approximately from 5.3 um to 7.8 um (bands 132-152 in Honeyside256).
I have tested various gas combinations, and it seems that only this pair is impacted. I don't know why. It is derived from HITRAN, which is trustworthy, so maybe there's some issue in the spectral file generation.
As a workaround, I have disabled O2 opacities in AGNI through the variable atmosphere.BLACKLIST_RT. It is treated properly in most of the code, but the O2 mass mixing ratio passed to radiance_calc is always set to zero.
The literature source for this continuum can be found here: https://opg.optica.org/ao/fulltext.cfm?uri=ao-36-3-563&id=60415
Resolved by replacing O2 with HCN in Honeyside spectral file. O2 opacity is quite low, and FastChem indicates that HCN abundances can be quite large. HCN has significant optical opacity.