title: getBluetoothLeAdvertiser() returns null
body: <pre><code>BluetoothLeAdvertiser advertiser = BluetoothAdapter.getDefaultAdapter().getBluetoothLeAdvertiser();
  </code></pre>
  
  <p>This returns null. I have tried on an API 21 and on an API 23 device, but with the same result. I have no idea what I am missing?</p>
  
  <p>The app builds and runs just fine, until of course the advertiser is used and the app crashes.</p>
  
  <p>I appreciate any help provided! :)</p>