don't take for granted that all anchor tags have an href attribute

app/assets/javascripts/application.js

@@ -92,7 +92,7 @@
     // `hashchange` is not triggered when link target is already in window.location
     $body.on('click', 'a', function() {
       var href = this.getAttribute('href');
-      if (href.indexOf('#') === 0 && href.substr(1) === gl.utils.getLocationHash()) {
+      if (href && href.indexOf('#') === 0 && href.substr(1) === gl.utils.getLocationHash()) {
         setTimeout(gl.utils.handleLocationHash, 1);
       }
     });