fix: Headroom console error when no header

wowchemy/assets/js/wowchemy-headroom.js

@@ -7,16 +7,19 @@
 
 import Headroom from './_vendor/headroom.min.js';
 
-let pageData = JSON.parse(document.getElementById('page-data').textContent);
-console.debug(`Use headroom on this page? ${pageData['use_headroom']}`);
+document.addEventListener('DOMContentLoaded', function () {
+  // Get config
+  let pageData = JSON.parse(document.getElementById('page-data').textContent);
+  console.debug(`Use headroom on this page? ${pageData['use_headroom']}`);
 
-if (pageData['use_headroom'] === true) {
-  document.addEventListener('DOMContentLoaded', function () {
-    // Grab header element
-    let myElement = document.querySelector('header');
+  // Grab header element
+  let $header = document.querySelector('header');
+
+  // Use Headroom on this page?
+  if ($header && pageData['use_headroom'] === true) {
     // Construct an instance of Headroom, passing the header
-    let headroom = new Headroom(myElement);
+    let headroom = new Headroom($header);
     // Initialise Headroom
     headroom.init();
-  });
-}
+  }
+});