Ensures that device admins are properly registered

If you register a broadcast receiver which acts as a device admin, you must also register an <intent-filter> for the action android.app.action.DEVICE_ADMIN_ENABLED, without any <data>, such that the device admin can be activated/deactivated.

To do this, add
<intent-filter>
<action android:name="android.app.action.DEVICE_ADMIN_ENABLED" />
</intent-filter>
to your <receiver>.