### 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)
if (margin_drawing_enabled) {
				Color margin_drawing_color(0.25, 1, 1, 0.63);
				real_t margin_drawing_width = 1;
				if (is_current()) {
					margin_drawing_width = 3;
				}
				Transform2D inv_camera_transform = get_camera_transform().affine_inverse();
				Size2 screen_size = _get_camera_screen_size();
				Vector2 margin_endpoints[4] = {
					inv_camera_transform.xform(Vector2((screen_size.width / 2) - ((screen_size.width / 2) * drag_margin[SIDE_LEFT]), (screen_size.height / 2) - ((screen_size.height / 2) * drag_margin[SIDE_TOP]))),
					inv_camera_transform.xform(Vector2((screen_size.width / 2) + ((screen_size.width / 2) * drag_margin[SIDE_RIGHT]), (screen_size.height / 2) - ((screen_size.height / 2) * drag_margin[SIDE_TOP]))),
					inv_camera_transform.xform(Vector2((screen_size.width / 2) + ((screen_size.width / 2) * drag_margin[SIDE_RIGHT]), (screen_size.height / 2) + ((screen_size.height / 2) * drag_margin[SIDE_BOTTOM]))),
					inv_camera_transform.xform(Vector2((screen_size.width / 2) - ((screen_size.width / 2) * drag_margin[SIDE_LEFT]), (screen_size.height / 2) + ((screen_size.height / 2) * drag_margin[SIDE_BOTTOM])))
				};
				Transform2D inv_transform = get_global_transform().affine_inverse(); 
				for (int i = 0; i < 4; i++) {
					draw_line(inv_transform.xform(margin_endpoints[i]), inv_transform.xform(margin_endpoints[(i + 1) % 4]), margin_drawing_color, margin_drawing_width);
				}
			}
		} break;
#endif
	}
}
void Camera2D::set_offset(const Vector2 &p_offset) {
	offset = p_offset;
	Point2 old_smoothed_camera_pos = smoothed_camera_pos;
	_update_scroll();
	smoothed_camera_pos = old_smoothed_camera_pos;
}
Vector2 Camera2D::get_offset() const {