queryAssignedNodes doesn't correctly locate default slot

[arthurevans]

Description

Currently, if you use the queryAssignedNodes decorator with no argument, it retrieves the first <slot> in the template, whether or not it has a name attribute.

For example, given the code:

@queryAssignedNodes()
defaultNodes;

render() {
  return html`
     <slot name="header"></slot>
    <slot></slot>
    <slot name="footer"></slot>
}

The defaultNodes parameter returns the contents of the first slot, not the second, as you'd expect.