### 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)
if (!handle_input_locally) {
		ERR_FAIL_COND_V(!is_inside_tree(), false);
		const Viewport *vp = this;
		while (true) {
			if (Object::cast_to<Window>(vp)) {
				break;
			}
			if (!vp->get_parent()) {
				break;
			}
			vp = vp->get_parent()->get_viewport();
		}
		if (vp != this) {
			return vp->is_input_handled();
		}
	}
	return local_input_handled;
}
void Viewport::set_handle_input_locally(bool p_enable) {