Error "Cannot read property 'el' of undefined" in production mode

[chenhaihong]

Version

3.0.0

Reproduction link

https://github.com/chenhaihong/vue-next-runtime-core-error

Steps to reproduce

1. Use @vue/cli to create a new project.
2. Put the code into your page's template

<pre>
      <!-- <code class="javascript" v-hljs>const a = 100;</code> -->
      <code class="javascript">const a = 100;</code>
</pre>

3. run yarn build
4. run http-server ./dist
5. visit the page
6. error happens now.

What is expected?

It should wokr with the same as

<pre>
      <code class="javascript">const a = 100;</code>
</pre>

What is actually happening?

runtime-core.esm-bundler.js?5c40:2020 Uncaught TypeError: Cannot read property 'el' of undefined
at cloneIfMounted (runtime-core.esm-bundler.js?5c40:2020)
at mountChildren (runtime-core.esm-bundler.js?5c40:4178)
at mountElement (runtime-core.esm-bundler.js?5c40:4103)
at processElement (runtime-core.esm-bundler.js?5c40:4075)
at patch (runtime-core.esm-bundler.js?5c40:3988)
at mountChildren (runtime-core.esm-bundler.js?5c40:4180)
at mountElement (runtime-core.esm-bundler.js?5c40:4103)
at processElement (runtime-core.esm-bundler.js?5c40:4075)
at patch (runtime-core.esm-bundler.js?5c40:3988)
at componentEffect (runtime-core.esm-bundler.js?5c40:4493)