### 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)
ERR_FAIL_INDEX(p_quadrant, 4);
	ERR_FAIL_INDEX(p_subdiv, SHADOW_ATLAS_QUADRANT_SUBDIV_MAX);
	if (positional_shadow_atlas_quadrant_subdiv[p_quadrant] == p_subdiv) {
		return;
	}
	positional_shadow_atlas_quadrant_subdiv[p_quadrant] = p_subdiv;
	static const int subdiv[SHADOW_ATLAS_QUADRANT_SUBDIV_MAX] = { 0, 1, 4, 16, 64, 256, 1024 };
	RS::get_singleton()->viewport_set_positional_shadow_atlas_quadrant_subdivision(viewport, p_quadrant, subdiv[p_subdiv]);
}
Viewport::PositionalShadowAtlasQuadrantSubdiv Viewport::get_positional_shadow_atlas_quadrant_subdiv(int p_quadrant) const {
	ERR_FAIL_INDEX_V(p_quadrant, 4, SHADOW_ATLAS_QUADRANT_SUBDIV_DISABLED);
	return positional_shadow_atlas_quadrant_subdiv[p_quadrant];
}
Transform2D Viewport::_get_input_pre_xform() const {
	const Window *this_window = Object::cast_to<Window>(this);
	if (this_window) {
		return this_window->window_transform.affine_inverse();
	}
	return Transform2D();
}
Ref<InputEvent> Viewport::_make_input_local(const Ref<InputEvent> &ev) {
	if (ev.is_null()) {
		return ev; 
	}
	Transform2D ai = get_final_transform().affine_inverse();
	return ev->xformed_by(ai);
}
Vector2 Viewport::get_mouse_position() const {