leaflet-src.js:1582 Uncaught (in promise) TypeError: Cannot read properties of undefined

This is a really strange error I am getting when adding Leaflet marker(s) to my Vue.js App.
Below is the code I am using:

<LMarker
    v-for="listing in listings"
        :latlng="[listing.lat, listing.lon]"
>
    <ChildVue />   
</LMarker>

When I remove ChildVue, the code works perfectly.
When I add back in ChildVue, I get the below:

leaflet-src.js:1582 Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'lat')

It’s odd because my ChildVue looks like this currently, with no calls to lat:

<template>
    <LPopup>
        <p>Hello world!</p>
    </LPopup>   
</template>

<script>
import { LPopup } from 'vue3-leaflet';
import 'leaflet/dist/leaflet.css';

export default {
  components: {
    LPopup
  },
};
</script>

Why does adding this file lead to this error?
Also, when I put the code of ChildVue.vue into my parent, the code works perfectly fine…