### 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)

}
		if (blend_time > 0) {
			Blend b;
			b.data = c.current;
			b.blend_time = b.blend_left = blend_time;
			c.blend.push_back(b);
		} else {
			c.blend.clear();
		}
	}
	if (get_current_animation() != p_name) {
		_clear_audio_streams();
		_stop_playing_caches(false);
	}
	c.current.from = &animation_set[name];
	if (c.assigned != name) { 
		c.current.pos = p_from_end ? c.current.from->animation->get_length() : 0;
	} else {
		if (p_from_end && c.current.pos == 0) {
			
			c.current.pos = c.current.from->animation->get_length();
		} else if (!p_from_end && c.current.pos == c.current.from->animation->get_length()) {
			
			c.current.pos = 0;
		}
	}
	c.current.speed_scale = p_custom_scale;
	c.assigned = name;
	c.seeked = false;
	c.started = true;