title: Android GCM : GCMRegistrar gives empty registration ID
body: <p>I have followed <a href="http://developer.android.com/guide/google/gcm/gs.html#server-app" rel="nofollow">http://developer.android.com/guide/google/gcm/gs.html#server-app</a> to implement GCM in my application</p>
  
  <pre><code>                    GCMRegistrar.checkDevice(this);
          GCMRegistrar.checkManifest(this);
          if (GCMRegistrar.isRegistered(this)) {
              Log.d(TAG, GCMRegistrar.getRegistrationId(this));
          }
          final String regId = GCMRegistrar.getRegistrationId(this);
  
          if (regId.equals("")) {
              GCMRegistrar.register(this, sender_id);
              Log.d(TAG, "Registration id :  "+GCMRegistrar.getRegistrationId(this));
          }
              else {
              Log.d("info", "already registered as" + regId);
          }
  </code></pre>
  
  <p>that returns empty string as registration ID
  what else is needed to get the registration ID??</p>