gz: fix [-Wunused-private-field], [-Wdouble-promotion] errors on OSX

src/modules/simulation/gz_bridge/GZGimbal.cpp

@@ -226,7 +226,7 @@ void GZGimbal::publishDeviceAttitude()
 void GZGimbal::publishJointCommand(gz::transport::Node::Publisher &publisher, const float att_stp, const float rate_stp,
 				   float &last_stp, const float min_stp, const float max_stp, const float dt)
 {
-	gz::msgs::Double msg;
+	gz::msgs::Float msg;
 
 	float new_stp = computeJointSetpoint(att_stp, rate_stp, last_stp, dt);
 	new_stp = math::constrain(new_stp, min_stp, max_stp);

src/modules/simulation/gz_bridge/GZMixingInterfaceServo.cpp

@@ -117,8 +117,8 @@ bool GZMixingInterfaceServo::init(const std::string &model_name)
 			return false;
 		}
 
-		double min_val = get_servo_angle_min(i);
-		double max_val = get_servo_angle_max(i);
+		double min_val = (double)get_servo_angle_min(i);
+		double max_val = (double)get_servo_angle_max(i);
 		_angle_min_rad.push_back(min_val);
 		_angular_range_rad.push_back(max_val - min_val);
 	}

src/modules/simulation/gz_plugins/moving_platform_controller/MovingPlatformController.cpp

@@ -240,7 +240,7 @@ void MovingPlatformController::updateWrenchCommand(
 
 		if (accel_xy > max_accel) {
 			const float scaling = max_accel / accel_xy;
-			_force += feedback_force * gz::math::Vector3d(scaling, scaling, 1.);
+			_force += feedback_force * gz::math::Vector3d((double)scaling, (double)scaling, 1.);
 
 		} else {
 			_force += feedback_force;

src/modules/simulation/gz_plugins/optical_flow/OpticalFlowSensor.hpp

@@ -64,8 +64,8 @@ class OpticalFlowSensor : public gz::sensors::Sensor
 	int _integration_time_us;
 
 	// Camera
-	double _horizontal_fov {0.0};
-	double _vertical_fov {0.0};
+	//double _horizontal_fov {0.0};
+	//double _vertical_fov {0.0};
 
 	cv::Mat _last_image_gray;
 	uint32_t _last_image_timestamp {0};