### 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)

cd.speed_scale *= -1.0;
				looped_flag = Animation::LOOPED_FLAG_END;
			}
			next_pos = Math::pingpong(next_pos, (double)len);
		} break;
		default:
			break;
	}
	double prev_pos = cd.pos; 
	cd.pos = next_pos;
	AnimationData *prev_from = cd.from;
	_animation_process_animation(cd.from, prev_pos, cd.pos, delta, p_blend, &cd == &playback.current, p_seeked, p_started, looped_flag);
	
	if (cd.from->animation->get_loop_mode() == Animation::LOOP_NONE) {
		if (prev_from != playback.current.from) {
			return; 
		}
		if (!backwards && prev_pos <= len && next_pos == len) {
			
			end_reached = true;
			end_notify = prev_pos < len; 
		}
		if (backwards && prev_pos >= 0 && next_pos == 0) {
			
			end_reached = true;
			end_notify = prev_pos > 0; 
		}
	}
}
void AnimationPlayer::_animation_process2(double p_delta, bool p_started) {