Tutorial - How to change firmware on 8u2

My code now looks like this:

for (;;)
      {
            HID_Device_USBTask(&Joystick_HID_Interface);
            USB_USBTask();
            
            if (Serial_IsCharReceived() && !dataReceived)
                  {
                  sensorIdentification =Serial_RxByte();
                  dataReceived = true;
                  }
            
            if (Serial_IsCharReceived() && dataReceived)
                  {
                  uint8_t data = Serial_RxByte();
                  
                  if             (sensorIdentification == "a") {sensorA =  data;}
                  else if (sensorIdentification == "b") {sensorB =  data;}
                  else if (sensorIdentification == "c") {sensorC =  data;}
                  else if (sensorIdentification == "d") {sensorD =  data;}
                  
                  dataReceived = false;
                  }

      }

In the callback

USB_JoystickReport_Data_t* JoystickReport = (USB_JoystickReport_Data_t*)ReportData;

JoystickReport->X  =  sensorA;
JoystickReport->Y  =  sensorB;
JoystickReport->Z  =  sensorC;
JoystickReport->Rz =  sensorD;


*ReportSize = sizeof(USB_JoystickReport_Data_t);
      return false; 
}

But the values don't update in any way.
When I run make, I get some warnings though.

warning: comparison with string literal results in unspecified behavior
warning: comparison between pointer and integer

Could this be the source of my problems?