### 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)

found_route = true;
					break;
				}
			}
		}
		if (found_route) {
			break;
		}
		open_list.erase(least_cost_transition);
	}
	
	if (found_route) {
		
		StringName at = travel;
		while (at != current) {
			new_path.push_back(at);
			at = cost_map[at].prev;
		}
		new_path.reverse();
		
		
		
		String current_path = current;
		int len = new_path.size() + 1;
		for (int i = 0; i < len; i++) {
			Ref<AnimationNodeStateMachine> anodesm = p_state_machine->find_node_by_path(current_path);
			if (anodesm.is_valid() && anodesm->get_state_machine_type() == AnimationNodeStateMachine::STATE_MACHINE_TYPE_GROUPED) {
				Ref<AnimationNodeStateMachinePlayback> playback = p_tree->get(base_path + current_path + "/playback");
				ERR_FAIL_COND_V(!playback.is_valid(), false);
				playback->_set_base_path(base_path + current_path + "/");