Issue #3515733 by mably: Avoid javascript error when tacjs config not available

Closes #3515733

js/main.js

@@ -16,6 +16,9 @@
     attach: function attach() {
       if (window.alreadyLaunch) return;
 
+      // Drupal tacjs configuration is required.
+      if (!drupalSettings.tacjs) return;
+
       // Set base URL for TacJS Log
       tarteaucitron.baseUrl = drupalSettings.path.baseUrl;