### 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)
Camera3D *first = nullptr;
				for (Camera3D *E : camera_3d_set) {
					if (first == nullptr || first->is_greater_than(E)) {
						first = E;
					}
				}
				if (first) {
					first->make_current();
				}
			}
#endif 
		} break;
		case NOTIFICATION_EXIT_TREE: {
			_gui_cancel_tooltip();
			RenderingServer::get_singleton()->viewport_set_scenario(viewport, RID());
			RenderingServer::get_singleton()->viewport_remove_canvas(viewport, current_canvas);
			if (contact_2d_debug.is_valid()) {
				RenderingServer::get_singleton()->free(contact_2d_debug);
				contact_2d_debug = RID();
			}
			if (contact_3d_debug_multimesh.is_valid()) {
				RenderingServer::get_singleton()->free(contact_3d_debug_multimesh);
				RenderingServer::get_singleton()->free(contact_3d_debug_instance);
				contact_3d_debug_instance = RID();
				contact_3d_debug_multimesh = RID();
			}
			remove_from_group("_viewports");
			set_physics_process_internal(false);
			RS::get_singleton()->viewport_set_active(viewport, false);