Messages with an element that may not be present in the scene

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Hi,

I'm creating a message that describes a vision result, where an element to grasp that may or may not be present in the scene.

# The timestamp of the capture
int timestamp 0
# Scene elements
Solid object_to_grasp
bool found_an_object_to_grasp
Solid[] obstacles
# Current pose
geometry_msgs/Pose current_tcp_pose
float64[] current_joints_pose

The solid is a complex type:

geometry_msgs/Pose center
geometry_msgs/Pose grasp_pose
Voxel[] voxels
float64 confidence

The issue with my message is that the "object_to_grasp" parameter cannot be filled if no object was found.

I'm not sure of what will happen if I feed None in the python interface of the client:

self.request:Scene.Request = Scene.Request()
request.object_to_grasp = None

And then send that to the server...

Will the code crash? Will the server find it and return None ?

Can I use this design, or shall I use a design with 2 distinct messages, with and without the object to grasp?

Thanks