android: fix the error (#549)

[outofmemory]

Please read and follow the issue templates:

1. Bug Report or Documentation Issue or Questions and Help? YES
2. Which react-native-wechat version are you using? 1.9.12
3. What platform does your issue occur on? (Android/iOS/Both) android
4. Please provide a clear and concise description of what the bug is as precisely as possible，you can:

Logs from Sentry：

java.lang.NullPointerException: Attempt to invoke interface method 'boolean com.tencent.mm.sdk.openapi.IWXAPI.handleIntent(android.content.Intent, com.tencent.mm.sdk.openapi.IWXAPIEventHandler)' on a null object reference
    at com.theweflex.react.WeChatModule.handleIntent(WeChatModule.java:2)
    at com.xxxx.xxxx.wxapi.WXEntryActivity.onCreate(WXEntryActivity.java:2)
    at android.app.Activity.performCreate(Activity.java:6355)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2440)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2547)
    at android.app.ActivityThread.access$1100(ActivityThread.java:151)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1398)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:157)
    at android.app.ActivityThread.main(ActivityThread.java:5603)
    at java.lang.reflect.Method.invoke(Method.java)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:774)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:652)

Your Environment

software	version
react-native-wechat	^ 1.9.12
react-native	^ 2.0.1
node	^ 12.14.1.
npm or yarn	^ 6.13.7

[aoarashi1988]

Actually , this issue is probably occered when you use apis without registerApp