### Godot version

4.0.beta13

### System information

Windows 10

### Issue description

When you call the `seek()` function without a current animation it outputs `Condition "!playback.current.from" is true.` to the debugger.

I was getting the error above whenever I would call `stop()` on an AnimationPlayer when it didn't have a playing animation. I realized that `stop()` also calls the `seek()` function.

I would expect the `seek()` and `stop()` functions to just do nothing, instead of throwing errors, if there isn't a current animation, or at least show an error that says that there is no animation to seek/stop.

This is the same issue that was described here: [#6122](https://github.com/godotengine/godot/issues/6122)

### Steps to reproduce

- Create an AnimationPlayer node.
- Don't have it play any animations.
- Call the `seek()` function.

### Minimal reproduction project

[seek_issue.zip](https://github.com/godotengine/godot/files/10442071/seek_issue.zip)

StringName name = p_name;
	if (String(name) == "") {
		name = playback.assigned;
	}
	ERR_FAIL_COND_MSG(!animation_set.has(name), vformat("Animation not found: %s.", name));
	Playback &c = playback;
	if (c.current.from) {
		double blend_time = 0.0;
		
		BlendKey bk;
		bk.from = c.current.from->name;
		bk.to = name;
		if (p_custom_blend >= 0) {
			blend_time = p_custom_blend;
		} else if (blend_times.has(bk)) {
			blend_time = blend_times[bk];
		} else {
			bk.from = "*";
			if (blend_times.has(bk)) {
				blend_time = blend_times[bk];
			} else {
				bk.from = c.current.from->name;
				bk.to = "*";
				if (blend_times.has(bk)) {
					blend_time = blend_times[bk];
				}
			}
		}
		if (p_custom_blend < 0 && blend_time == 0 && default_blend_time) {
			blend_time = default_blend_time;