when add the head configuration like favicon in the .config.js, build error。

[Jinwan5290]

code as follows
module.exports = { base: '/docs/', title: 'mrapi', description: 'mrapi docs', head: ['link', { rel: 'icon', href: '/assets/favico.ico' }], ... }
and dev is ok
but when i build
The error occurred：
`
TypeError: undefined is not a function
at /Users/jinwan/Desktop/work-project/mrapi-docs/node_modules/@vuepress/core/lib/node/build/index.js:101:15
at Array.filter ()
at Build.render (/Users/jinwan/Desktop/work-project/mrapi-docs/node_modules/@vuepress/core/lib/node/build/index.js:101:8)
at async App.build (/Users/jinwan/Desktop/work-project/mrapi-docs/node_modules/@vuepress/core/lib/node/App.js:499:5)
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

`
then I enter the source code to view
and see

in the debug
we can see there is no function called userHeadTags on the this instance

so how can solve this

[Jinwan5290]

sorry I wrote it wrongly