Can't get VNode when use named slot

[MirckMuse]

Version

3.0.0-alpha.8

Steps to reproduce

Create a component named TButton

<template>
  <button><slot/></button>
</template>

Create a component named TPopover

<template>
  <span>
    <div ref="popover" id="tooltip" role="tooltip">
      <slot>{{content}}</slot>
    </div>

    <slot name="reference"/>
  </span>
</template>

<script>
import { onMounted, ref } from 'vue'
export default {
  name: 'TPopover',
  props: {
    content: { type: String, default: '' },
    placement: { type: String, default: 'bottom' },
    showArrow: { type: Boolean, default: true }
  },
  setup (props, { slots}) {
    const popover = ref(null)
    onMounted(() => {
      console.log(slots.reference()[0].el) // Print null, can't get the VNode of button
    })
    return {
      popover
    }
  }
}
</script>

using named slot

<t-popover>
  <div>
    popover content
  </div>
  <template #reference>
	<t-button>button</t-button>
  </template>
</t-popover>

What is expected?

Get the named slot's VNode

What is actually happening?

Get null

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