### 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)

String prop_name = p_name;
	if (prop_name.begins_with("states/")) {
		String node_name = prop_name.get_slicec('/', 1);
		String what = prop_name.get_slicec('/', 2);
		if (what == "node") {
			Ref<AnimationNode> anode = p_value;
			if (anode.is_valid()) {
				add_node(node_name, p_value);
			}
			return true;
		}
		if (what == "position") {
			if (states.has(node_name)) {
				states[node_name].position = p_value;
			}
			return true;
		}
	} else if (prop_name == "transitions") {
		Array trans = p_value;
		ERR_FAIL_COND_V(trans.size() % 3 != 0, false);
		for (int i = 0; i < trans.size(); i += 3) {
			add_transition(trans[i], trans[i + 1], trans[i + 2]);
		}
		return true;
	} else if (prop_name == "graph_offset") {
		set_graph_offset(p_value);
		return true;
	}