[custom elements api] TypeError: Cannot read properties of null (reading 'insertBefore') using v-if on named slot

[wolandec]

Vue version

3.5.13

Link to minimal reproduction

https://play.vuejs.org/#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

Steps to reproduce

• create a custom element with named slot based on Vue 3 component
• create a wrapper component using that custom element
• use wrapper and put v-if condition on using of the named slot
• start with false condition for displaying
• changing the condition to true causes an exception

What is expected?

v-if condition works well and named slot is working as expected

What is actually happening?

exception thrown and named slot content is never shown

System Info

Any additional comments?

No response