[Android] Crash on rewards tipping

[SergeyZhukovsky]

I found that crash in backtrace on a stable 1.49.122 version. It's unknown why that could happen. Most likely Activity was on a state to be destroyed or was destroying. We would better catch NullPointerException and ignore it.
For verifying just make sure that tips go through.

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setAlpha(float)' on a null object reference
        at org.chromium.chrome.browser.rewards.BraveRewardsTipConfirmationListener.V2(BraveRewardsTipConfirmationListener.java:5)
        at org.chromium.chrome.browser.BraveRewardsNativeWorker.onBalance(BraveRewardsNativeWorker.java:571)
        at android.os.MessageQueue.nativePollOnce(Native Method)
        at android.os.MessageQueue.next(MessageQueue.java:335)
        at android.os.Looper.loopOnce(Looper.java:186)
        at android.os.Looper.loop(Looper.java:313)
        at android.app.ActivityThread.main(ActivityThread.java:8669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:571)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1135)

[kjozwiak]

The above requires 1.50.121 or higher for 1.50.x verification 👍

[GeetaSarvadnya]

Verification PASSED on Vivo X70 Pro version 12 running Bravemonoarm64.apk_1.50.121

Ensured that one-time/monthly tipping worked without any crashes/obvious issues as per the following:

Example	Example	Example	Example	Example