core-collapse sets core-list's selected to null when triggered

[yawhide]

Hello,

So I am trying to figure out why the core-list's selected property is being set to null when I trigger my core-collapse component. Here is my code:

<core-list data='{{data}}'>
  <template>
    {{selected}}, {{index}}
    <core-collapse id='coreCollapse' opened="{{selected}}" fixedSize>
    <div id='someId'>
        hi
    </div>
    </core-collapse>
  </template>
</core-list>

so when I inspect the core-list component in chrome dev tools, {{selected}} is null, when clicked {{selected}} goes true, collapse gets triggered, then {{selected}} goes back to null, and collapse gets triggered again.

I removed core-collapse and {{selected}} stays true when clicked.

How do I fix this behaviour? Is this a bug?