gpgs.leaderboard_get_player_score() crashes if player has no score on leaderboard

[britzl]

E  Process: com.defold.extension.gpgs, PID: 20763
E  java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.String com.google.android.gms.games.leaderboard.LeaderboardScore.getDisplay
   Rank()' on a null object reference
E      at com.defold.gpgs.GpgsJNI.scoreToJSON(GpgsJNI.java:624)
E      at com.defold.gpgs.GpgsJNI.access$1700(GpgsJNI.java:53)
E      at com.defold.gpgs.GpgsJNI$12.onSuccess(GpgsJNI.java:701)
E      at com.defold.gpgs.GpgsJNI$12.onSuccess(GpgsJNI.java:695)
E      at com.google.android.gms.tasks.zzn.run(Unknown Source:4)
E      at android.os.Handler.handleCallback(Handler.java:883)
E      at android.os.Handler.dispatchMessage(Handler.java:100)
E      at android.os.Looper.loop(Looper.java:224)
E      at android.app.ActivityThread.main(ActivityThread.java:7520)
E      at java.lang.reflect.Method.invoke(Native Method)
E      at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
E      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)