Extra bridge creation in launch files

[nkoenig]

I copied this bug report from #791.

---

I also probably found a bug in

subt/subt_ros/launch/vehicle_topics.launch

Lines 140 to 166 in 6bd98e3

	<group unless="$(arg stereo_cam)">
	<node
	pkg="ros_ign_bridge"
	type="parameter_bridge"
	name="ros_ign_bridge_camera"
	args="$(arg sensor_prefix)/camera_front/camera_info@sensor_msgs/CameraInfo[ignition.msgs.CameraInfo">
	<remap from="$(arg sensor_prefix)/camera_front/camera_info" to="front/camera_info"/>
	</node>
	<node
	pkg="ros_ign_image"
	type="image_bridge"
	name="ros_ign_image_camera"
	args="$(arg sensor_prefix)/camera_front/image">
	<remap from="$(arg sensor_prefix)/camera_front/image" to="front/image_raw"/>
	</node>
	<node
	pkg="subt_ros"
	type="optical_frame_publisher"
	name="optical_frame_publisher">
	<remap from="input/image" to="front/image_raw" />
	<remap from="output/image" to="front/optical/image_raw" />
	<remap from="input/camera_info" to="front/camera_info" />
	<remap from="output/camera_info" to="front/optical/camera_info" />
	</node>
	</group>

.

It begins with a block unless="$(arg stereo_cam)" and adds a RGB camera. But the models which use RGBD camera do not include this additional RGB camera (i.e. X4_SENSOR_CONFIG_2). However, bridges for the RGB cam are created. I only protected the set_rate bridge with the additional unless="$(arg rgbd_cam)", but I think the whole RGB camera block should be excluded when the RGBD is present. But I felt that doing such change could break something I did not foresee, so I did not do it.