title: "Broken @import" error with grunt build?
body: <p>I am trying to build my first angular application. I am using yeoman and angular-generator. The app run fine with "grunt serve" but when I ran "grunt build" the process stops with the error -</p>
  
  <pre><code>Running "cssmin:generated" (cssmin) task
  Warning: Broken @import declaration of "" Use --force to continue.
  
  Aborted due to warnings.
  </code></pre>
  
  <p>I am not sure what is the cause of this error. I have looked everywhere but could not find a solution.
  Here are the css links -</p>
  
  <pre><code> &lt;!-- build:css(.) styles/vendor.css --&gt;
      &lt;!-- bower:css --&gt;
      &lt;link rel="stylesheet" href="bower_components/bootstrap/dist/css/bootstrap.css" /&gt;
      &lt;link rel="stylesheet" href="bower_components/animate.css/animate.css" /&gt;
      &lt;!-- endbower --&gt;
      &lt;!-- endbuild --&gt;
      &lt;!-- build:css(.tmp) styles/main.css --&gt;
      &lt;link rel="stylesheet" href="styles/main.css"&gt;
      &lt;link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.4.0/css/font-awesome.min.css"&gt;
      &lt;link href="https://fonts.googleapis.com/css?family=Bungee|Carrois+Gothic+SC|Oswald" rel="stylesheet"&gt;
      &lt;base href="/"&gt;
      &lt;!-- endbuild --&gt;
  </code></pre>