fix: ensure html attributes

Author: egoist

lib/parseComponent.js

@@ -186,6 +186,7 @@ module.exports = (content, opts) => {
         tree => {
           for (const node of tree) {
             if (node.tag) {
+              node.attrs = node.attrs || {}
               const existing =
                 node.attrs[':style'] || node.attrs['v-bind:style']
               node.attrs[':style'] = `$options.style(this, ${existing})`