fix error handler

src/main.rs

@@ -473,8 +473,8 @@ impl<const TOWER_HEIGHT: usize> Game<TOWER_HEIGHT> {
     }
 
     fn ask_tower(&self, msg: &str) -> io::Result<Input> {
-        let mut res = String::new();
         loop {
+            let mut res = String::new();
             print!("{msg} (enter a tower number, exit, clear or undo):");
             stdout().flush()?;
             stdin().read_line(&mut res)?;