pbmview - qoi decoding issue

[STPR]

Hello,
While searching some qoi files to test your viewer, I've found an issue talking about an edge case in some qoi decoders:
phoboslab/qoi#258

And, like a lot of others decoders, your decoder fail to decode one of the file correctly.
The background of the file edgecase.qoi must be fully opaque black:
https://qoiformat.org/qoi_test_images.zip

[skeeto]

Thanks! This should be fixed by not skipping the table insertion on runs, though that makes runs slightly more expensive. Now that I'm aware of the edge case, I wish the specification had set the first color to all zeros like the table itself.