(FIX) Check default SMS app before delete inbox sms

[datnguyen92]

On certain phones (e.g. Huawei Mate 8 running Nougat), if SMSSync is not the default SMS app, the app will crash when execute method delSmsFromInbox(). Below is the stack trace for this issue:

FATAL EXCEPTION: SmsReceiverService
Process: org.addhen.smssync.debug, PID: 11676
java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.
    at android.database.CursorWindow.nativeGetLong(Native Method)
    at android.database.CursorWindow.getLong(CursorWindow.java:511)
    at android.database.AbstractWindowedCursor.getLong(AbstractWindowedCursor.java:90)
    at android.database.CursorWrapper.getLong(CursorWrapper.java:127)
    at org.addhen.smssync.smslib.sms.ProcessSms.getThreadIdKitKat(ProcessSms.java:273)
    at org.addhen.smssync.smslib.sms.ProcessSms.getThreadId(ProcessSms.java:237)
    at org.addhen.smssync.smslib.sms.ProcessSms.delSmsFromInbox(ProcessSms.java:127)
    at org.addhen.smssync.data.message.ProcessMessage.deleteFromSmsInbox(ProcessMessage.java:198)
    at org.addhen.smssync.data.message.PostMessage.routeSms(PostMessage.java:147)
    at org.addhen.smssync.presentation.service.SmsReceiverService.handleSmsReceived(SmsReceiverService.java:275)
    at org.addhen.smssync.presentation.service.SmsReceiverService$ServiceHandler.handleMessage(SmsReceiverService.java:339)
    at android.os.Handler.dispatchMessage(Handler.java:111)
    at android.os.Looper.loop(Looper.java:207)
    at android.os.HandlerThread.run(HandlerThread.java:61)

In order to void that, I propose to check the default SMS app before deleting inbox message

[datnguyen92]

@eyedol Would you mind to have a look? Just a small fix but may prevent crashes