title: build dev failed: Cannot set property 'fileSystem' of null
body: <p>I am trying to run an Ionic 2 Application. I am getting following error on running <code>ionic serve</code></p>
  
  <blockquote>
    <p>build dev failed: Cannot set property 'fileSystem' of null</p>
  </blockquote>
  
  <p>The complete log is as below:</p>
  
  <pre><code>λ ionic serve                                                              
  
  &gt; ionic-hello-world@ ionic:serve D:\ionic         
  &gt; ionic-app-scripts serve                                                  
  
  [18:11:23]  ionic-app-scripts 0.0.47                                       
  [18:11:24]  watch started ...                                              
  [18:11:24]  build dev started ...                                          
  [18:11:24]  clean started ...                                              
  [18:11:24]  clean finished in 6 ms                                         
  [18:11:24]  copy started ...                                               
  [18:11:24]  transpile started ...                                          
  [18:11:28]  transpile finished in 4.15 s                                   
  [18:11:28]  webpack started ...                                            
  [18:11:28]  build dev failed: Cannot set property 'fileSystem' of null     
  [18:11:28]  dev server running: http://localhost:8100/                     
  
  [18:11:28]  copy finished in 4.39 s                                        
  [18:11:28]  watch ready in 4.44 s   
  </code></pre>