### Godot version

v4.0.3.stable.official [5222a99f5]

### System information

Mac

### Issue description

The following code will not print any vertices, nor polygons. 
The `NavigationMesh` resource will not be saved correctly.

Even though we specify `bake_navigation_mesh(false)` (on the main thread)

```gdscript
func _ready() -> void:
	var navreg = $NavigationRegion3D
	navreg.bake_navigation_mesh(false)
	
	print(navreg.navmesh.get_vertices())
	print(navreg.navmesh.get_polygon_count())

	var to_save = preload("res://testresource.gd").new(navreg.navmesh)
	ResourceSaver.save(
		to_save,
		"output.tres",
		ResourceSaver.SaverFlags.FLAG_BUNDLE_RESOURCES
	)
```

### Steps to reproduce

1. Download minimal repo below
2. Run the repo
3. Check the console
4. Check `output.tres`

<img width="316" alt="Screenshot 2023-06-03 at 19 05 22" src="https://github.com/godotengine/godot/assets/100964/83ea661d-1c5a-4044-b9cc-2a5434a89280">

<img width="1028" alt="Screenshot 2023-06-03 at 19 05 34" src="https://github.com/godotengine/godot/assets/100964/cb099d0c-f626-48a4-b4f4-9a57b7988df1">


### Minimal reproduction project

[test-navmesh.zip](https://github.com/godotengine/godot/files/11642578/test-navmesh.zip)

if (enabled_edge_lines) {
			for (int polygon_indices_index = 0; polygon_indices_index < polygon_indices_size; polygon_indices_index++) {
				line_vertex_array_ptrw[line_vertex_index] = vertices[polygon_indices[polygon_indices_index]];
				line_vertex_index += 1;
				if (polygon_indices_index + 1 == polygon_indices_size) {
					line_vertex_array_ptrw[line_vertex_index] = vertices[polygon_indices[0]];
					line_vertex_index += 1;
				} else {
					line_vertex_array_ptrw[line_vertex_index] = vertices[polygon_indices[polygon_indices_index + 1]];
					line_vertex_index += 1;
				}
			}
		}
	}
	Ref<StandardMaterial3D> face_material = NavigationServer3D::get_singleton()->get_debug_navigation_geometry_face_material();
	Array face_mesh_array;
	face_mesh_array.resize(Mesh::ARRAY_MAX);
	face_mesh_array[Mesh::ARRAY_VERTEX] = face_vertex_array;
	if (enabled_geometry_face_random_color) {
		face_mesh_array[Mesh::ARRAY_COLOR] = face_color_array;
	}
	debug_mesh->add_surface_from_arrays(Mesh::PRIMITIVE_TRIANGLES, face_mesh_array);
	debug_mesh->surface_set_material(0, face_material);
	if (enabled_edge_lines) {
		Ref<StandardMaterial3D> line_material = NavigationServer3D::get_singleton()->get_debug_navigation_geometry_edge_material();
		Array line_mesh_array;
		line_mesh_array.resize(Mesh::ARRAY_MAX);
		line_mesh_array[Mesh::ARRAY_VERTEX] = line_vertex_array;
		debug_mesh->add_surface_from_arrays(Mesh::PRIMITIVE_LINES, line_mesh_array);
		debug_mesh->surface_set_material(1, line_material);