Condition SDL counts so we don't pass negative numbers to new

Should address #4425

src/Joystick/JoystickSDL.cc

@@ -49,7 +49,7 @@ QMap<QString, Joystick*> JoystickSDL::discover(MultiVehicleManager* _multiVehicl
             SDL_JoystickClose(sdlJoystick);
 
             qCDebug(JoystickLog) << "\t" << name << "axes:" << axisCount << "buttons:" << buttonCount << "hats:" << hatCount << "isGC:" << isGameController;
-            ret[name] = new JoystickSDL(name, axisCount, buttonCount, hatCount, i, isGameController, _multiVehicleManager);
+            ret[name] = new JoystickSDL(name, qMax(0,axisCount), qMax(0,buttonCount), qMax(0,hatCount), i, isGameController, _multiVehicleManager);
         } else {
             qCDebug(JoystickLog) << "\tSkipping duplicate" << name;
         }