### 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_input_as_handled"), &Viewport::set_input_as_handled);
	ClassDB::bind_method(D_METHOD("is_input_handled"), &Viewport::is_input_handled);
	ClassDB::bind_method(D_METHOD("set_handle_input_locally", "enable"), &Viewport::set_handle_input_locally);
	ClassDB::bind_method(D_METHOD("is_handling_input_locally"), &Viewport::is_handling_input_locally);
	ClassDB::bind_method(D_METHOD("set_default_canvas_item_texture_filter", "mode"), &Viewport::set_default_canvas_item_texture_filter);
	ClassDB::bind_method(D_METHOD("get_default_canvas_item_texture_filter"), &Viewport::get_default_canvas_item_texture_filter);
	ClassDB::bind_method(D_METHOD("set_embedding_subwindows", "enable"), &Viewport::set_embedding_subwindows);
	ClassDB::bind_method(D_METHOD("is_embedding_subwindows"), &Viewport::is_embedding_subwindows);
	ClassDB::bind_method(D_METHOD("set_canvas_cull_mask", "mask"), &Viewport::set_canvas_cull_mask);
	ClassDB::bind_method(D_METHOD("get_canvas_cull_mask"), &Viewport::get_canvas_cull_mask);
	ClassDB::bind_method(D_METHOD("set_canvas_cull_mask_bit", "layer", "enable"), &Viewport::set_canvas_cull_mask_bit);
	ClassDB::bind_method(D_METHOD("get_canvas_cull_mask_bit", "layer"), &Viewport::get_canvas_cull_mask_bit);
	ClassDB::bind_method(D_METHOD("set_default_canvas_item_texture_repeat", "mode"), &Viewport::set_default_canvas_item_texture_repeat);
	ClassDB::bind_method(D_METHOD("get_default_canvas_item_texture_repeat"), &Viewport::get_default_canvas_item_texture_repeat);
	ClassDB::bind_method(D_METHOD("set_sdf_oversize", "oversize"), &Viewport::set_sdf_oversize);
	ClassDB::bind_method(D_METHOD("get_sdf_oversize"), &Viewport::get_sdf_oversize);
	ClassDB::bind_method(D_METHOD("set_sdf_scale", "scale"), &Viewport::set_sdf_scale);
	ClassDB::bind_method(D_METHOD("get_sdf_scale"), &Viewport::get_sdf_scale);
	ClassDB::bind_method(D_METHOD("set_mesh_lod_threshold", "pixels"), &Viewport::set_mesh_lod_threshold);
	ClassDB::bind_method(D_METHOD("get_mesh_lod_threshold"), &Viewport::get_mesh_lod_threshold);
	ClassDB::bind_method(D_METHOD("_process_picking"), &Viewport::_process_picking);
#ifndef _3D_DISABLED
	ClassDB::bind_method(D_METHOD("set_world_3d", "world_3d"), &Viewport::set_world_3d);
	ClassDB::bind_method(D_METHOD("get_world_3d"), &Viewport::get_world_3d);
	ClassDB::bind_method(D_METHOD("find_world_3d"), &Viewport::find_world_3d);
	ClassDB::bind_method(D_METHOD("set_use_own_world_3d", "enable"), &Viewport::set_use_own_world_3d);
	ClassDB::bind_method(D_METHOD("is_using_own_world_3d"), &Viewport::is_using_own_world_3d);
	ClassDB::bind_method(D_METHOD("get_camera_3d"), &Viewport::get_camera_3d);
	ClassDB::bind_method(D_METHOD("set_as_audio_listener_3d", "enable"), &Viewport::set_as_audio_listener_3d);
	ClassDB::bind_method(D_METHOD("is_audio_listener_3d"), &Viewport::is_audio_listener_3d);