### Godot version

v4.1.rc2.official [46424488e]

### System information

Godot v4.1.rc2 - Windows 10.0.22621 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3060 (NVIDIA; 31.0.15.3623) - AMD Ryzen 7 5700G with Radeon Graphics (16 Threads)

### Issue description

When setting the AnimationTree to active, Godot crashes.

### Steps to reproduce

https://github.com/godotengine/godot/assets/46705245/dbe5eb81-1357-43e8-ac80-a4eb97eea9fc

### Minimal reproduction project

[Crash.zip](https://github.com/godotengine/godot/files/11945826/Crash.zip)

states.clear();
	transitions.clear();
	playback = "playback";
	start_node = "Start";
	end_node = "End";
	graph_offset = Vector2();
	Ref<AnimationNodeStartState> s;
	s.instantiate();
	State start;
	start.node = s;
	start.position = Vector2(200, 100);
	states[start_node] = start;
	Ref<AnimationNodeEndState> e;
	e.instantiate();
	State end;
	end.node = e;
	end.position = Vector2(900, 100);
	states[end_node] = end;
	emit_changed();
	emit_signal(SNAME("tree_changed"));
}
void AnimationNodeStateMachine::set_node_position(const StringName &p_name, const Vector2 &p_position) {
	ERR_FAIL_COND(!states.has(p_name));
	states[p_name].position = p_position;
}
Vector2 AnimationNodeStateMachine::get_node_position(const StringName &p_name) const {
	ERR_FAIL_COND_V(!states.has(p_name), Vector2());
	return states[p_name].position;
}
void AnimationNodeStateMachine::_tree_changed() {