title: Crash with urbanairship in android (when app is not in foreground)
body: <p>Hi i am getting crashed when app is not in foreground or when we press back key to send app to back stack. And later when app receives the push notification from server at that point app crashes.
  below is the stack trace of crash happneing</p>
  
  <p>And help would be helpfull.</p>
  
  <hr>
  
  <pre><code>01-13 16:46:17.329: E/UA AP(16021): Failed to load meta-data, NullPointer: null
  01-13 16:46:17.330: E/UA AP(16021): Unable to takeOff automatically
  01-13 16:46:17.338: W/dalvikvm(16021): threadid=1: thread exiting with uncaught exception (group=0x411609a8)
  01-13 16:46:17.348: E/AndroidRuntime(16021): FATAL EXCEPTION: main
  01-13 16:46:17.348: E/AndroidRuntime(16021): java.lang.RuntimeException: Unable to start receiver com.urbanairship.push.GCMPushReceiver: java.lang.NullPointerException
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2520)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at android.app.ActivityThread.access$1500(ActivityThread.java:156)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1416)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at android.os.Handler.dispatchMessage(Handler.java:99)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at android.os.Looper.loop(Looper.java:153)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at android.app.ActivityThread.main(ActivityThread.java:5299)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at java.lang.reflect.Method.invokeNative(Native Method)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at java.lang.reflect.Method.invoke(Method.java:511)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:115)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at dalvik.system.NativeStart.main(Native Method)
  01-13 16:46:17.348: E/AndroidRuntime(16021): Caused by: java.lang.NullPointerException
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at com.urbanairship.push.PushService.acquireWakeLock(Unknown Source)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at com.urbanairship.push.PushService.runGcmIntentInService(Unknown Source)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at com.urbanairship.push.GCMPushReceiver.onReceive(Unknown Source)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2513)
  01-13 16:46:17.348: E/AndroidRuntime(16021):    ... 11 more
  01-13 16:46:19.153: I/Process(16021): Sending signal. PID: 16021 SIG: 9
  </code></pre>