Fix cannot read property 'parentNode' of null

Author: route

lib/capybara/cuprite/javascripts/index.js

@@ -97,7 +97,7 @@ class Cuprite {
   path(node) {
     let nodes = [node];
     let parent = node.parentNode;
-    while (parent !== document) {
+    while (parent !== document || parent !== null) {
       nodes.unshift(parent);
       parent = parent.parentNode;
     }