### Godot version

4.2 1ba920f

### System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 30.0.15.1403) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

### Issue description

```GDScript
func _ready() -> void:
	$AnimationPlayer.play("new_animation")
	$AnimationPlayer.advance(0)
```
The animation has a single track with Update Mode set to discrete. It does not play, no matter the argument used.
Removing `advance()` will make it play.

Works correctly in rc1.

### Steps to reproduce

1. Run MRP on master
2. Run MRP in 4.2 rc1

### Minimal reproduction project

[brokedvance.zip](https://github.com/godotengine/godot/files/13460977/brokedvance.zip)

AnimationMixer::_animation_removed(p_name, p_library);
	StringName name = p_library == StringName() ? p_name : StringName(String(p_library) + "/" + String(p_name));
	if (!animation_set.has(name)) {
		return; 
	}
	_animation_set_cache_update();
	
	List<BlendKey> to_erase;
	for (const KeyValue<BlendKey, double> &E : blend_times) {
		BlendKey bk = E.key;
		if (bk.from == name || bk.to == name) {
			to_erase.push_back(bk);
		}
	}
	while (to_erase.size()) {
		blend_times.erase(to_erase.front()->get());
		to_erase.pop_front();
	}
}
void AnimationPlayer::_rename_animation(const StringName &p_from_name, const StringName &p_to_name) {