Fix: fix the 'undefined' string in the css file issue.

[fubupc]

There is an incorrect 'undefined' string in the css file after processing by
source-map-loader.

It's caused by the line

callback(null, input.replace(match[0], match[2]), map);

There are two kinds of comment format regex1 and regex2. regex1 only have one capture group so match[2] will be undefined. So maybe just replace by empty would be OK?

[sokra]

Thanks

[fubupc]

@sokra No thanks :)

BTW, could you update the package on www.npmjs.com? I found that I can't update the package using npm update.

Thanks!