Fix problem showing dropdown after window resize

When the browser window is resized, a new click event listener is added
to the window but the old one is not removed. The old one ends up
preventing the newly-made dropdown from opening.

Fix this by remembering the click event listener function added to the
window, and remove it before making the new dropdown after a window
resize.

assets/js/dropdown.js

@@ -16,6 +16,7 @@
         });
     }
 
+    var windowClickListener;
     const makeDropdown = function () {
         if (mediaQuery.matches) return;
         const submenuItems = [];
@@ -62,11 +63,12 @@
             document.body.classList.toggle('is-dropdown-open');
         });
 
-        window.addEventListener('click', function (e) {
+        windowClickListener = function (e) {
             if (!toggle.contains(e.target) && document.body.classList.contains('is-dropdown-open')) {
                 document.body.classList.remove('is-dropdown-open');
             }
-        });
+        };
+        window.addEventListener('click', windowClickListener);
     }
 
     imagesLoaded(head, function () {
@@ -75,6 +77,7 @@
 
     window.addEventListener('resize', function () {
         setTimeout(function () {
+            window.removeEventListener('click', windowClickListener);
             nav.innerHTML = navHTML;
             makeDropdown();
         }, 1);