### 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)
panel->set_theme_type_variation(SNAME("TooltipPanel"));
	
	
	Control *base_tooltip = tooltip_owner->make_custom_tooltip(tooltip_text);
	
	if (!base_tooltip) {
		gui.tooltip_label = memnew(Label);
		gui.tooltip_label->set_theme_type_variation(SNAME("TooltipLabel"));
		gui.tooltip_label->set_auto_translate(gui.tooltip_control->is_auto_translating());
		gui.tooltip_label->set_text(tooltip_text);
		base_tooltip = gui.tooltip_label;
		panel->connect("mouse_entered", callable_mp(this, &Viewport::_gui_cancel_tooltip));
	}
	base_tooltip->set_anchors_and_offsets_preset(Control::PRESET_FULL_RECT);
	panel->set_transient(true);
	panel->set_flag(Window::FLAG_NO_FOCUS, true);
	panel->set_flag(Window::FLAG_POPUP, false);
	panel->set_flag(Window::FLAG_MOUSE_PASSTHROUGH, true);
	panel->set_wrap_controls(true);
	panel->add_child(base_tooltip);
	panel->gui_parent = this;
	gui.tooltip_popup = panel;
	tooltip_owner->add_child(gui.tooltip_popup);
	Point2 tooltip_offset = GLOBAL_GET("display/mouse_cursor/tooltip_position_offset");
	Rect2 r(gui.tooltip_pos + tooltip_offset, gui.tooltip_popup->get_contents_minimum_size());
	r.size = r.size.min(panel->get_max_size());
	Window *window = gui.tooltip_popup->get_parent_visible_window();
	Rect2i vr;
	if (gui.tooltip_popup->is_embedded()) {
		vr = gui.tooltip_popup->_get_embedder()->get_visible_rect();