I found some crash issues

[YYYSSSHHH]

Environment Info：
APK version 4.4 (13)
AndroidOS Version = 6.0.1

Description information：
We find that mobile apps are prone to crashes due to a network issue, mainly because successful network API calls return unexpected or no data.
And we found that when this app's network returned data is empty, or some fields are null (JSON format), the app has crashed.

crash information：
Crash One:

crashActivity=org.asdtm.goodweather.MainActivity
:
java.lang.NumberFormatException: Invalid float: "null"
at java.lang.StringToReal.invalidReal(StringToReal.java:63)
at java.lang.StringToReal.initialParse(StringToReal.java:164)
at java.lang.StringToReal.parseFloat(StringToReal.java:323)
at java.lang.Float.parseFloat(Float.java:306)
at org.asdtm.goodweather.e.a(dalvik_source_goodweather_13.apk)
at org.asdtm.goodweather.widget.MoreWidgetService.onHandleIntent(dalvik_source_goodweather_13.apk)
at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:66)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.os.HandlerThread.run(HandlerThread.java:61)

Crash Two:
crashActivity=org.asdtm.goodweather.MainActivity
:
java.lang.StringIndexOutOfBoundsException: length=0; regionStart=0; regionLength=1
at java.lang.String.startEndAndLength(String.java:298)
at java.lang.String.substring(String.java:1087)
at org.asdtm.goodweather.model.b$c.a(dalvik_source_goodweather_13.apk)
at org.asdtm.goodweather.e.a(dalvik_source_goodweather_13.apk)
at org.asdtm.goodweather.widget.MoreWidgetService.onHandleIntent(dalvik_source_goodweather_13.apk)
at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:66)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.os.HandlerThread.run(HandlerThread.java:61)

Finally：
The cause of the program crash may be that the network response data is not handled properly in the code, such as null.
If you have confirmed or fixed this problem, please give me a reply, thank you!

[YYYSSSHHH]

How do we test the APP?
We use the fuzzing method to simulate the network response data. For example, when the app receives network API response data from server or network, we will replace it with 404, null and random data.
#A very simple example:
normal data ：Value=”hello” -----fuzzing-----> simulated data ：Value=null or network request fails（404、503） or Value=”heee”(random data) or Value=""(empty) , etc.