### 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)

}
	}
	if (stop_request) {
		start_request = StringName();
		travel_request = StringName();
		path.clear();
		playing = false;
		return 0;
	}
	if (!playing && start_request != StringName() && travel_request != StringName()) {
		return 0;
	}
	
	if (start_request != StringName() || travel_request != StringName()) {
		if (p_state_machine->get_state_machine_type() != AnimationNodeStateMachine::STATE_MACHINE_TYPE_GROUPED) {
			_clear_path_children(tree, p_state_machine, p_test_only);
		}
	}
	if (start_request != StringName()) {
		path.clear();
		String start_target = _validate_path(p_state_machine, start_request);
		Vector<String> start_path = String(start_target).split("/");
		start_request = start_path[0];
		if (start_path.size()) {
			_start_children(tree, p_state_machine, start_target, p_test_only);
		}
		
		if (p_state_machine->states.has(start_request)) {
			_start(p_state_machine);
		} else {