### Godot version

v4.0.beta.custom_build [0a9e6e478]

### System information

Ubuntu, Nvidia, Vulkan

### Issue description

When a Camera2D is freed - either explicitly or by being a child of a scene that is being switched away from via a method like `get_tree().change_scene_to_file()` - then this camera somehow stays active instead of Godot properly switching to no-camera-mode.

`get_viewport().get_camera_2d()` then returns all sorts of funny things from `<Freed Object>`  (it's supposed to return `null`) to arbitrary nodes of the current scene (not cameras).

This can lead to crashes.

### Steps to reproduce

checkout the MRP.

note that the "Go to scene 2" button switches places after pressing it.
that is because a camera is still active that does not exist in the current tree.

restart it a couple of times and spam the "Go to scene 2" button.
notice the garbage output.

### Minimal reproduction project

[godot_4_camera_bug.zip](https://github.com/godotengine/godot/files/10560455/godot_4_camera_bug.zip)
contact_2d_debug = RenderingServer::get_singleton()->canvas_item_create();
				RenderingServer::get_singleton()->canvas_item_set_parent(contact_2d_debug, find_world_2d()->get_canvas());
#ifndef _3D_DISABLED
				PhysicsServer3D::get_singleton()->space_set_debug_contacts(find_world_3d()->get_space(), get_tree()->get_collision_debug_contact_count());
				contact_3d_debug_multimesh = RenderingServer::get_singleton()->multimesh_create();
				RenderingServer::get_singleton()->multimesh_allocate_data(contact_3d_debug_multimesh, get_tree()->get_collision_debug_contact_count(), RS::MULTIMESH_TRANSFORM_3D, false);
				RenderingServer::get_singleton()->multimesh_set_visible_instances(contact_3d_debug_multimesh, 0);
				RenderingServer::get_singleton()->multimesh_set_mesh(contact_3d_debug_multimesh, get_tree()->get_debug_contact_mesh()->get_rid());
				contact_3d_debug_instance = RenderingServer::get_singleton()->instance_create();
				RenderingServer::get_singleton()->instance_set_base(contact_3d_debug_instance, contact_3d_debug_multimesh);
				RenderingServer::get_singleton()->instance_set_scenario(contact_3d_debug_instance, find_world_3d()->get_scenario());
				RenderingServer::get_singleton()->instance_geometry_set_flag(contact_3d_debug_instance, RS::INSTANCE_FLAG_DRAW_NEXT_FRAME_IF_VISIBLE, true);
#endif 
				set_physics_process_internal(true);
			}
		} break;
		case NOTIFICATION_READY: {
#ifndef _3D_DISABLED
			if (audio_listener_3d_set.size() && !audio_listener_3d) {
				AudioListener3D *first = nullptr;
				for (AudioListener3D *E : audio_listener_3d_set) {
					if (first == nullptr || first->is_greater_than(E)) {
						first = E;
					}
				}
				if (first) {
					first->make_current();
				}
			}
			if (camera_3d_set.size() && !camera_3d) {