Indent attribute doesn't seem to be handled correctly

[indianakernick]

I have this indented paragraph:

<p class="ql-indent-1">Text</p>

When this is converted to a sequence of delta ops via Quill's clipboard module, the result is this:

[
  {
    insert: 'Text\n',
    attributes: { indent: 1 }
  }
]

As far as I can tell, this is valid. It was generated by Quill itself so I expect it to be valid. However, when this sequence of delta ops is converted back to HTML using 0.12.1 and the default configuration, the result is this:

<p class="ql-indent-1"><br/></p>
<p class="ql-indent-1"><br/></p>

I would have expected a round trip from HTML to delta to HTML to leave me back where I started, or close enough that it doesn't matter.