Fixed js browser incompatibility

(cherry picked from commit 86ff2dac05412a6ff994968c2be6122a7fcf85f9)

assets/js/just-the-docs.js

@@ -26,7 +26,7 @@ jtd.onReady = function(ready) {
 function initNav() {
   jtd.addEvent(document, 'click', function(e){
     var target = e.target;
-    while (target && target.classList && !target.classList.contains('nav-list-expander')) {
+    while (target && !(target.classList && target.classList.contains('nav-list-expander'))) {
       target = target.parentElement;
     }
     if (target) {