title: Bug with image picker with flutter on ImageSource.Gallery
body: <h2>Info:</h2>
  <ol>
  <li>Package: image_picker plugin for flutter, version 0.6.3+1</li>
  <li>Android build only, no IOS</li>
  </ol>
  <h2>Problem:</h2>
  <p><em>This is my method to pick an image:</em></p>
  <pre><code>  Future&lt;void&gt; pickImage(ImageSource source) async {
      File selected = await ImagePicker.pickImage(source: source);
      print(selected?.path);
      imageFilePath = selected?.path ?? imageFilePath;
    }
  </code></pre>
  <p>=&gt; When using ImageSource.gallery, when choosing a picture which is not in cache, 'selected.path' prints null. When selecting a picture which is in cache, it does retrieve it, 'selected.path' prints:</p>
  <pre><code>/data/user/0/be.etnic.parrainage_mcf/cache/image_picker2517179621202627006.jpg
  </code></pre>
  <p><strong>Anyone knows what causes this problem and how I can solve it?</strong></p>
  <h2>Sidenotes:</h2>
  <ol>
  <li>I can also pick an image by making a picture directly with ImageSource.camera, this doesn't give me any problems.</li>
  <li>I'm not 100% sure that the selected pictures that return null
  are not in cache, but the pictures that do return correctly from
  choosing from the ImageSource.gallery all come from that
  cache-folder</li>
  <li>I don't have any permissions set in my AndroidManifest.xml
  (other than Internet permission)</li>
  </ol>