refactor: consolidate status code assignment logic

Replace two separate if statements with an else-if chain to:

- Make err.status precedence over err.statusCode explicit

- Avoid unnecessary assignment when both properties exist

Author: Ayoub-Mabrouk

index.js

@@ -84,14 +84,10 @@ exports = module.exports = function errorHandler (options) {
   }
 
   return function errorHandler (err, req, res, next) {
-    // respect err.statusCode
-    if (err.statusCode) {
-      res.statusCode = err.statusCode
-    }
-
-    // respect err.status
     if (err.status) {
       res.statusCode = err.status
+    } else if (err.statusCode) {
+      res.statusCode = err.statusCode
     }
 
     // default status code to 500