\0, \9 and url(/my/path) without quotes breaks the parser

[olemarius]

Examples
The following cases cause error when parsing css files.
margin-top: 1px \9; // IE8-9
width: 220px \0; //IE9 and below

In my case the \9 hack is used in boostrap3, and \0 hack is used in boostrap-select plugin, so the workaround would be a find a way to strip the lines containing these hacks and add '' to url().

[olemarius]

Workaround is to use https://github.com/ben-eb/stylehacks or wait for cssnano to support this in v4.2 cssnano/cssnano#263