NullPointerException (Null Pointer->Crash)：未判断服务端返回数据是否为空导致的应用崩溃

[liyansong2018]

[scenario]
网络异常时，直接登录，触发崩溃

[Analysis]
没有对收到的http报文进行判空操作

[Suggestions]

199行代码之后，判断 loginUrl 是否为空，如果空，则弹窗或者直接报错，不进行后续的登录流程

[Log]

beyond1q:/data/system/dropbox # cat data_app_crash@1631422710856.txt
Process: me.yluo.ruisiapp
Flags: 0x28c8be44
Package: me.yluo.ruisiapp v40 (2.9.8.2)
Foreground: Yes
Build: samsung/dream2qltezh/dream2qltechn:7.1/N2G48H/G9550ZHU1AQEE:user/release-keys

java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.startsWith(java.lang.String)' on a null 
object reference
        at me.yluo.ruisiapp.myhttp.HttpUtil.getUrl(HttpUtil.java:18)
        at me.yluo.ruisiapp.myhttp.HttpUtil.post(HttpUtil.java:40)
        at me.yluo.ruisiapp.activity.LoginActivity.startLogin(LoginActivity.java:255)
        at me.yluo.ruisiapp.activity.LoginActivity.lambda$onCreate$0$LoginActivity(LoginActivity.java:100)
        at me.yluo.ruisiapp.activity.-$$Lambda$LoginActivity$x9wErgAks3boUA8rdIy9PIUWvTQ.onClick(lambda)
        at android.view.View.performClick(View.java:5638)
        at android.view.View$PerformClick.run(View.java:22430)
        at android.os.Handler.handleCallback(Handler.java:751)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6198)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:891)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:781)