Handle undefined Github access token

app/routes/signup/github.js

@@ -1,5 +1,6 @@
 import Route from '@ember/routing/route';
 import { inject as service } from '@ember/service';
+import { isEmpty } from '@ember/utils';
 
 export default Route.extend({
 
@@ -8,7 +9,17 @@ export default Route.extend({
   redirect () {
     this._super(...arguments);
 
-    const accessToken = window.location.hash.match(/access_token=(.+)/)[1];
+    let accessToken;
+    try {
+      accessToken = window.location.hash.match(/access_token=(.+)/)[1];
+    } catch (error) { /* ignore */ }
+
+    if (isEmpty(accessToken) || accessToken === 'undefined') {
+      console.error('No GitHub access token found.');
+      this.transitionTo('signup');
+      return;
+    }
+
     this.kredits.set('githubAccessToken', accessToken);
 
     this.transitionTo('signup.eth-account');