Wrap last return statement in else to fix tree shaking (#27788)

## Bug

- [x] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

fixes #27744

packages/next/shared/lib/router/router.ts

@@ -103,9 +103,9 @@ export function getDomainLocale(
       }${locale === detectedDomain.defaultLocale ? '' : `/${locale}`}${path}`
     }
     return false
+  } else {
+    return false
   }
-
-  return false
 }
 
 export function addLocale(