### 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)

playing = true;
	_set_current(p_state_machine, start_request != StringName() ? start_request : p_state_machine->start_node);
	teleport_request = true;
	stop_request = false;
	start_request = StringName();
}
bool AnimationNodeStateMachinePlayback::_travel(AnimationTree *p_tree, AnimationNodeStateMachine *p_state_machine, bool p_is_allow_transition_to_self, bool p_test_only) {
	return _make_travel_path(p_tree, p_state_machine, p_is_allow_transition_to_self, path, p_test_only);
}
String AnimationNodeStateMachinePlayback::_validate_path(AnimationNodeStateMachine *p_state_machine, const String &p_path) {
	if (p_state_machine->get_state_machine_type() == AnimationNodeStateMachine::STATE_MACHINE_TYPE_GROUPED) {
		return p_path; 
	}
	String target = p_path;
	Ref<AnimationNodeStateMachine> anodesm = p_state_machine->find_node_by_path(target);
	while (anodesm.is_valid() && anodesm->get_state_machine_type() == AnimationNodeStateMachine::STATE_MACHINE_TYPE_GROUPED) {
		Vector<int> indices = anodesm->find_transition_from(anodesm->start_node);
		if (indices.size()) {
			target = target + "/" + anodesm->get_transition_to(indices[0]); 
		} else {
			break; 
		}
		anodesm = p_state_machine->find_node_by_path(target);
	}
	return target;
}
bool AnimationNodeStateMachinePlayback::_make_travel_path(AnimationTree *p_tree, AnimationNodeStateMachine *p_state_machine, bool p_is_allow_transition_to_self, Vector<StringName> &r_path, bool p_test_only) {