fix: cannot read properties of null in toggleViewsHints (#9736)

Author: michalsn

system/Debug/Toolbar/Views/toolbar.js

@@ -337,6 +337,11 @@ var ciDebugBar = {
         const OUTER_ELEMENTS = ["HTML", "BODY", "HEAD"];
 
         var getValidElementInner = function (node, reverse) {
+            // handle null node
+            if (node === null) {
+                return null;
+            }
+
             // handle invalid tags
             if (OUTER_ELEMENTS.indexOf(node.nodeName) !== -1) {
                 for (var i = 0; i < document.body.children.length; ++i) {