check node presence in inDoc

Author: yyx990803

src/util/dom.js

@@ -37,8 +37,9 @@ export function query (el) {
  */
 
 export function inDoc (node) {
+  if (!node) return false
   var doc = node.ownerDocument.documentElement
-  var parent = node && node.parentNode
+  var parent = node.parentNode
   return doc === node ||
     doc === parent ||
     !!(parent && parent.nodeType === 1 && (doc.contains(parent)))