fix(dom): in removeClass, check element for null in case of a disposed player (#6701)

Author: travisbader

src/js/utils/dom.js

@@ -282,6 +282,11 @@ export function addClass(element, classToAdd) {
  *         The DOM element with class name removed.
  */
 export function removeClass(element, classToRemove) {
+  // Protect in case the player gets disposed
+  if (!element) {
+    log.warn("removeClass was called with an element that doesn't exist");
+    return null;
+  }
   if (element.classList) {
     element.classList.remove(classToRemove);
   } else {