Fixed a NullPointerException in com.facebook.unity.FB.getKeyHash

[kabamwchang]

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Pull Request Details

This change fixes a rare NullPointerException crash on SM-T113 devices running Android OS 4.4.4 / API-19

Test Plan

This change has been pushed into production and verified through crash telemetry.

[kabamwchang]

I do not appear to have permissions to add labels, so I am unable to add the "bug" label.

[troy-lamerton]

This is still an issue with SDK v11.0.0 - 2021-06-05

Here is the stacktrace we're seeing:

java.lang.NullPointerException Attempt to get length of null array 
    SourceFile:5 com.facebook.unity.FB.getKeyHash()
    SourceFile:4 com.facebook.unity.FB$1.onInitialized()
    SourceFile:2 c.a.o.k()
    SourceFile:7 com.facebook.unity.FB.Init()
    Native Method com.unity3d.player.UnityPlayer.nativeRender()
    Unknown Source com.unity3d.player.UnityPlayer.access$300()
    Unknown Source:83 com.unity3d.player.UnityPlayer$e$1.handleMessage()
    Handler.java:102 android.os.Handler.dispatchMessage()
    Looper.java:201 android.os.Looper.loop()
    Unknown Source:20 com.unity3d.player.UnityPlayer$e.run()
    <00000000000000000000000000000000> UnityEngine.AndroidJNISafe.CheckException()
    <00000000000000000000000000000000> UnityEngine.AndroidJavaObject._CallStatic(System.String methodName, System.Object[] args)
    <00000000000000000000000000000000> Facebook.Unity.Mobile.Android.AndroidFacebook.Init(System.String appId, Facebook.Unity.HideUnityDelegate hideUnityDelegate, Facebook.Unity.InitDelegate onInitComplete)
    <00000000000000000000000000000000> Facebook.Unity.FB+OnDLLLoaded.Invoke()
    <00000000000000000000000000000000> Facebook.Unity.FB+CompiledFacebookLoader.Start()

For our app, this has happened on Android versions 10/9/8.1. Mostly HUAWEI and Vivo devices, but also some from Xiaomi and OnePlus devices.

I believe this pull request will fix the above crash so please consider merging this.

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