Coverage increased (+0.01%) to 98.802% when pulling d704b78cbd4b64496dc4cb15382802b74752ae87 on give-null-source-a-name into e583442cb19b7313e54c77de9b77bed79e1dd4bd on master.
Well, they aren't unmapped, they just don't have corresponding source. Webpack code is one with null source. I'll add a section to the README.
Or I'm totally missing source = null meaning
If mapping item source is
null
use[no source]
as filenameResolves #142