error handling for position

src/sprite.rs

@@ -1,5 +1,6 @@
 use crate::{from_base36, optional_data_line, AnimationFrames, Image, Position, ToBase36};
 use crate::image::animation_frames_from_string;
+use std::str::FromStr;
 
 #[derive(Debug, Eq, PartialEq)]
 pub struct Sprite {
@@ -82,7 +83,7 @@ impl From<String> for Sprite {
                     panic!("Bad room/position for sprite: {}", string);
                 }
 
-                position = Some(Position::from(room_position[1].to_string()).unwrap());
+                position = Some(Position::from_str(room_position[1]).unwrap());
             } else if last_line.starts_with("COL") {
                 colour_id = Some(last_line.replace("COL ", "").parse().unwrap());
             } else if last_line.starts_with("ITM") {