Use unwrap_or_else instead of unwrap_or

Clippy emits:

 warning: use of `unwrap_or` followed by a function call

As suggested use `unwrap_or_else`.

Author: tcharding

src/miniscript/types/mod.rs

@@ -526,7 +526,7 @@ pub trait Property: Sized {
                 });
 
                 res.map_err(|kind| Error {
-                    fragment: last_err_frag.unwrap_or(fragment.clone()),
+                    fragment: last_err_frag.unwrap_or_else(|| fragment.clone()),
                     error: kind,
                 })
             }