absmag_g_r column is incorrect

[NickyBfudd]

When requesting g-r colors in a query, u-g colours are instead returned.

To Reproduce

from marvin.tools.query import Query
q = Query(search_filter='nsa.z < 0.1', return_params=['absmag_g_r', 'nsa.elpetro_absmag'])
r = q.run()
r.results

From inspecting the outputs of r.results and comparing the g-r colors to the corresponding FNugriz magnitudes, it is apparent that 'absmag_g_r' is returning u-g colors.

Expected behaviour
'absmag_g_r' returns g-r colors.

Desktop (please complete the following information):

• masOS Big Sur, Version 11.7.3
• Version of Marvin: 2.8.0

Additional context
This issue is apparent in https://sdss-marvin.readthedocs.io/en/latest/tutorials/notebooks/Marvin_Results.html, in which the plotted range of g-r colors extends to significantly higher values than would be expected.