Fix 3D camera override when there is no camera in scene tree

[aryan-11825114]

Previously if there was no camera in the scene tree, on overriding the camera, it would receive no input, this P.R. fixes it.

Preview

Screencast.from.2024-12-21.18-27-25.webm

MRP

test.zip

[Hilderin]

The code looks great and it works when testing with the artefact build.

But it's impossible to select an element in the scene in 3D when there's no Camera3D.
My guess is this condition in RuntimeNodeSelect::_find_3d_items_at_pos:

Camera3D *camera = root->get_viewport()->get_camera_3d();
if (!camera) {
	return;
}

[aryan-11825114]

Selection seems to work on removing the condition, should I commit it in this P.R.

[Hilderin]

Yes, I think you should include it in this PR.

[aryan-11825114]

Changes made and rebased.

[Hilderin]

Superbe! Thanks!

[Repiteo]

Thanks!