### 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)
ClassDB::bind_method(D_METHOD("set_world_2d", "world_2d"), &Viewport::set_world_2d);
	ClassDB::bind_method(D_METHOD("get_world_2d"), &Viewport::get_world_2d);
	ClassDB::bind_method(D_METHOD("find_world_2d"), &Viewport::find_world_2d);
	ClassDB::bind_method(D_METHOD("set_canvas_transform", "xform"), &Viewport::set_canvas_transform);
	ClassDB::bind_method(D_METHOD("get_canvas_transform"), &Viewport::get_canvas_transform);
	ClassDB::bind_method(D_METHOD("set_global_canvas_transform", "xform"), &Viewport::set_global_canvas_transform);
	ClassDB::bind_method(D_METHOD("get_global_canvas_transform"), &Viewport::get_global_canvas_transform);
	ClassDB::bind_method(D_METHOD("get_final_transform"), &Viewport::get_final_transform);
	ClassDB::bind_method(D_METHOD("get_screen_transform"), &Viewport::get_screen_transform);
	ClassDB::bind_method(D_METHOD("get_visible_rect"), &Viewport::get_visible_rect);
	ClassDB::bind_method(D_METHOD("set_transparent_background", "enable"), &Viewport::set_transparent_background);
	ClassDB::bind_method(D_METHOD("has_transparent_background"), &Viewport::has_transparent_background);
	ClassDB::bind_method(D_METHOD("set_msaa_2d", "msaa"), &Viewport::set_msaa_2d);
	ClassDB::bind_method(D_METHOD("get_msaa_2d"), &Viewport::get_msaa_2d);
	ClassDB::bind_method(D_METHOD("set_msaa_3d", "msaa"), &Viewport::set_msaa_3d);
	ClassDB::bind_method(D_METHOD("get_msaa_3d"), &Viewport::get_msaa_3d);
	ClassDB::bind_method(D_METHOD("set_screen_space_aa", "screen_space_aa"), &Viewport::set_screen_space_aa);
	ClassDB::bind_method(D_METHOD("get_screen_space_aa"), &Viewport::get_screen_space_aa);
	ClassDB::bind_method(D_METHOD("set_use_taa", "enable"), &Viewport::set_use_taa);
	ClassDB::bind_method(D_METHOD("is_using_taa"), &Viewport::is_using_taa);
	ClassDB::bind_method(D_METHOD("set_use_debanding", "enable"), &Viewport::set_use_debanding);
	ClassDB::bind_method(D_METHOD("is_using_debanding"), &Viewport::is_using_debanding);
	ClassDB::bind_method(D_METHOD("set_use_occlusion_culling", "enable"), &Viewport::set_use_occlusion_culling);
	ClassDB::bind_method(D_METHOD("is_using_occlusion_culling"), &Viewport::is_using_occlusion_culling);
	ClassDB::bind_method(D_METHOD("set_debug_draw", "debug_draw"), &Viewport::set_debug_draw);
	ClassDB::bind_method(D_METHOD("get_debug_draw"), &Viewport::get_debug_draw);
	ClassDB::bind_method(D_METHOD("get_render_info", "type", "info"), &Viewport::get_render_info);
	ClassDB::bind_method(D_METHOD("get_texture"), &Viewport::get_texture);
	ClassDB::bind_method(D_METHOD("set_physics_object_picking", "enable"), &Viewport::set_physics_object_picking);
	ClassDB::bind_method(D_METHOD("get_physics_object_picking"), &Viewport::get_physics_object_picking);