I followed "GNSDK for Mobile Android Developers Guide" and tried to built the sample app on my android device. I specified my gnsdkClientId and gnsdkClientTag, and crated an empty license.txt file in my assets folder. The status on top of the Android sample UI still complains "gnsdk_manager_initialize: An invalide license was specified". Did I miss any step? should I put anything in the license.txt file?