[Bug] Functional components not rendering

[mornir]

I use this serializer to render external link:

<template functional>
  <a
    v-if="props.href && children[0] && children[0].text"
    :href="props.href"
    target="_blank"
    rel="noopener"
    class="underline"
  >
    <slot />
  </a>
</template>

When marking the link bold, the marked text is not rendered:

Expected

A bold link:

This component handles this case correctly:
https://github.com/nuxt-community/sanity-module/blob/main/src/components/sanity-content.ts