Add back button press handling on android

[no-dap]

Resolve #11

Android IamportActivity에서 webview가 생성된 후에 back button press 시 handleOnActivityResult로 null intent가 전달되면서
아래와 같은 에러가 발생합니다.

java.lang.NullPointerException: Attempt to invoke virtual method 'android.os.Bundle android.content.Intent.getExtras()' on a null object reference
        at kr.iamport.capacitor.IamportCapacitor.handleOnActivityResult(IamportCapacitor.java:45)
        at com.getcapacitor.Bridge.onActivityResult(Bridge.java:776)
        at com.getcapacitor.BridgeActivity.onActivityResult(BridgeActivity.java:214)
        at android.app.Activity.dispatchActivityResult(Activity.java:8110)
        at android.app.ActivityThread.deliverResults(ActivityThread.java:4838)

Full stacktrace

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.woot.wootAppRelease, PID: 13011
    java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=6018, result=0, data=null} to activity {com.woot.wootAppRelease/com.woot.wootAppRelease.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.os.Bundle android.content.Intent.getExtras()' on a null object reference
        at android.app.ActivityThread.deliverResults(ActivityThread.java:4845)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:4886)
        at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.os.Bundle android.content.Intent.getExtras()' on a null object reference
        at kr.iamport.capacitor.IamportCapacitor.handleOnActivityResult(IamportCapacitor.java:45)
        at com.getcapacitor.Bridge.onActivityResult(Bridge.java:776)
        at com.getcapacitor.BridgeActivity.onActivityResult(BridgeActivity.java:214)
        at android.app.Activity.dispatchActivityResult(Activity.java:8110)
        at android.app.ActivityThread.deliverResults(ActivityThread.java:4838)

[SoleeChoi]

안녕하세요 아임포트 기술지원팀입니다.

귀하의 PR에 힌트를 얻어 해당 버그 수정하였지만 보다 나은 해결 방법을 적용하게 되면서
안타깝게도 해당 PR은 머지되지 못했습니다. 양해 부탁드립니다.

적용된 코드는 아래에서 확인하실 수 있습니다.

• https://github.com/iamport/iamport-capacitor/blob/master/android/src/main/java/kr/iamport/capacitor/IamportActivity.java#L75
• https://github.com/iamport/iamport-capacitor/blob/master/android/src/main/java/kr/iamport/capacitor/IamportCapacitor.java#L48

감사합니다.