Update proguard rule

[longld103]

I got a crash report for Android application when publish it to Google Play store. It took me several hours of testing on multiple devices and I found out that the cause of the error was a missing rule in the progurad file.

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• CHANGELOG.md's "Unreleased" section has been updated, if applicable.

[JakeWharton]

What was the exception?

[longld103]

@JakeWharton This is the exception:

java.lang.ClassCastException
     FATAL EXCEPTION: main
Process: com.my.androidapp, PID: 22593
java.lang.ClassCastException
	at androidx.appcompat.app.p.a(SourceFile:1)
	at com.my.androidapp.main.LoadActivity$a.b(SourceFile:5)
	at q3.g$b$a$a.run(SourceFile:38)
	at android.os.Handler.handleCallback(Handler.java:938)
	at android.os.Handler.dispatchMessage(Handler.java:99)
	at android.os.Looper.loop(Looper.java:223)
	at android.app.ActivityThread.main(ActivityThread.java:7664)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

Below is the mapping file:

com.my.androidapp.main.LoadActivity$1 -> com.my.androidapp.main.LoadActivity$a:
# {"id":"sourceFile","fileName":"LoadActivity.java"}
    com.my.androidapp.main.LoadActivity this$0 -> a
    1:6:void <init>(com.my.androidapp.main.LoadActivity):67:67 -> <init>
    1:6:void onFailure(retrofit2.Call,java.lang.Throwable):92:92 -> a
      # {"id":"com.android.tools.r8.residualsignature","signature":"(Lq3/b;Ljava/lang/Throwable;)V"}
    1:10:void onResponse(retrofit2.Call,retrofit2.Response):71:71 -> b
      # {"id":"com.android.tools.r8.residualsignature","signature":"(Lq3/b;Lq3/r;)V"}
    11:15:void onResponse(retrofit2.Call,retrofit2.Response):85:85 -> b
    16:19:void onResponse(retrofit2.Call,retrofit2.Response):86:86 -> b