### 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)
return default_texture;
}
void Viewport::set_positional_shadow_atlas_size(int p_size) {
	positional_shadow_atlas_size = p_size;
	RS::get_singleton()->viewport_set_positional_shadow_atlas_size(viewport, p_size, positional_shadow_atlas_16_bits);
}
int Viewport::get_positional_shadow_atlas_size() const {
	return positional_shadow_atlas_size;
}
void Viewport::set_positional_shadow_atlas_16_bits(bool p_16_bits) {
	if (positional_shadow_atlas_16_bits == p_16_bits) {
		return;
	}
	positional_shadow_atlas_16_bits = p_16_bits;
	RS::get_singleton()->viewport_set_positional_shadow_atlas_size(viewport, positional_shadow_atlas_size, positional_shadow_atlas_16_bits);
}
bool Viewport::get_positional_shadow_atlas_16_bits() const {
	return positional_shadow_atlas_16_bits;
}
void Viewport::set_positional_shadow_atlas_quadrant_subdiv(int p_quadrant, PositionalShadowAtlasQuadrantSubdiv p_subdiv) {