Processing fails when reducing b-band continuum data and modifying detectormap

This was reported on the #drp-2d slack channel 2021-10-09 by Neven Caplar.

When running reduceExposure against b-band continuum data, the processing fails:

https://gist.github.com/nevencaplar/08d6532809090a9053b4a36b68ad38b0

This can be circumvented by setting photometerLines.doApertureCorrection=False, but this would mean that the processing would not yield an adjusted detectormap.

The basic problem is that continuum is not recognized as an lamp - nor there are procedures to process continuum data.  The image gets processed as sky frame and obviously line identification fails and detectorMap adjustment fails.

Please update the code to ensure that an adjusted detectormap can be generated while processing continuum data.