fix: sidebar title error (#1360)

* fix: sidebar title error

* Update sidebar.js

Author: sy-records

Diff for: src/core/event/sidebar.js

@@ -86,7 +86,7 @@ export function getAndActive(router, el, isParent, autoTitle) {
       const href = a.getAttribute('href');
       const node = isParent ? a.parentNode : a;
 
-      a.title = a.innerText;
+      a.title = a.title || a.innerText;
 
       if (hash.indexOf(href) === 0 && !target) {
         target = a;