in xcode debug ios, Message from debugger: Terminated due to signal 6

Question

I debug ios extension, when I use JSONSerialization.data, extension crash, and log is

Message from debugger: Terminated due to signal 6

It is strange that error can not catch , just terminated.

I tried much to find this on net but dont find any similer problem or any solution.. please need help soon....

my code:

      do {
       let payload = try JSONSerialization.data(withJSONObject: messageProperties, options: [])
       ........
      }
     catch {
        .....
      }