Allow `None` as a value in data_files.
Allow `None` as a value in data_files.

rec/BiblioPixel,ManiacalLabs/BiblioPixel,rec/BiblioPixel,ManiacalLabs/BiblioPixel,rec/BiblioPixel,ManiacalLabs/BiblioPixel,ManiacalLabs/BiblioPixel,rec/BiblioPixel