Corrected listing number from 9-10 to 9-13

src/ch12-03-improving-error-handling-and-modularity.md

@@ -228,7 +228,7 @@ out of bounds` message.
 arguments</span>
 
 This code is similar to [the `Guess::new` function we wrote in Listing
-9-10][ch9-custom-types]<!-- ignore -->, where we called `panic!` when the
+9-13][ch9-custom-types]<!-- ignore -->, where we called `panic!` when the
 `value` argument was out of the range of valid values. Instead of checking for
 a range of values here, we’re checking that the length of `args` is at least 3
 and the rest of the function can operate under the assumption that this