### 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)
}
								}
								HashMap<Pair<ObjectID, int>, uint64_t, PairHash<ObjectID, int>>::Iterator SF = physics_2d_shape_mouseover.find(Pair(res[i].collider_id, res[i].shape));
								if (!SF) {
									physics_2d_shape_mouseover.insert(Pair(res[i].collider_id, res[i].shape), frame);
									co->_mouse_shape_enter(res[i].shape);
								} else {
									SF->value = frame;
								}
							}
							if (send_event) {
								co->_input_event_call(this, ev, res[i].shape);
							}
						}
					}
				}
			}
			if (is_mouse) {
				_cleanup_mouseover_colliders(false, false, frame);
			}
		}
#ifndef _3D_DISABLED
		CollisionObject3D *capture_object = nullptr;
		if (physics_object_capture.is_valid()) {
			capture_object = Object::cast_to<CollisionObject3D>(ObjectDB::get_instance(physics_object_capture));
			if (!capture_object || !camera_3d || (mb.is_valid() && mb->get_button_index() == MouseButton::LEFT && !mb->is_pressed())) {
				physics_object_capture = ObjectID();
			}
		}
		if (pos == last_pos) {