Update dev-dependencies

Author: wooorm

lib/all.js

@@ -6,12 +6,11 @@ module.exports = all
 
 // Serialize all children of `parent`.
 function all(parent, config) {
-  var children = parent && parent.children
-  var length = children && children.length
+  var children = (parent && parent.children) || []
   var index = -1
   var results = []
 
-  while (++index < length) {
+  while (++index < children.length) {
     results[index] = one(children[index], config)
   }
 

package.json

@@ -41,7 +41,7 @@
     "tape": "^5.0.0",
     "unist-builder": "^2.0.0",
     "xastscript": "^2.0.0",
-    "xo": "^0.35.0"
+    "xo": "^0.38.0"
   },
   "scripts": {
     "format": "remark . -qfo && prettier . --write --loglevel warn && xo --fix",