Skip bad header keywords when making filter combos

[TheSkyentist]

This is a fix for #117 which was briefly mentioned in #182.
The bug only arises when multiple bands are combined to create detection images.

[TheSkyentist]

These keywords are included in the headers if the drizzled images are made with pipeline.auto_script.make_combined_mosaics and not aws.visit_processor.cutout_mosaic. So this doesn't affect mosaics built with visit_processor. The solution is either to skip the offending keywords as suggested here, or to rewrite the portions of make_combined_mosaics that include these header keywords to begin with.

[gbrammer]

I think it's fine to do the skip here, I was just requesting a slight rewording of the if test.

[TheSkyentist]

Yes, in this commit I'm only skipping the offending keywords which turn out to be either an empty string or HISTORY, rather than skipping the entire header assignment as was done in the previous PR. Is there still something to be improved?

[gbrammer]

Please see the tiny review request above for a little bit more flexible code which is otherwise identical to your update.

[TheSkyentist]

Oh I think only write-access members of a repository can see review requests, I'm not seeing anything popping up on my end. Perhaps I'm looking in the wrong place?

[gbrammer]

That's strange. I would have thought you could see the code review as the person who originally filed the PR. I edited the file myself with the requested change.