Unhandled error for [ng:cloak]

[alexewerlof]

Angular has a couple of CSS rules that take care of its cloaking feature and it looks like this:

[ng:cloak],
[ng-cloak],
[data-ng-cloak],
[x-ng-cloak],
.ng-cloak,
.x-ng-cloak {
  display: none !important;
}

Interestingly CSSO fails when it tries to parse those rules:

events.js:85
      throw er; // Unhandled 'error' event
            ^
TypeError: Cannot read property '0' of undefined

(same error as #233)

I noticed that the main issue is when [ng:cloak] is involved and when I eliminate it, CSSO doesn't crash.
Is it an erroneus CSS or should CSSO be able to handle it?