Fix doc test in on_debug.
@@ -1026,7 +1026,7 @@ impl Engine {
/// # Example
///
/// ```
- /// # fn main() -> Result<(), rhai::EvalAltResult> {
+ /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
/// # use std::sync::RwLock;
/// # use std::sync::Arc;
/// use rhai::Engine;
