Issue: Footnotes Not Reusable in vB

Sometimes it's useful to reuse the same reference for mulitple footnotes. It should be possible to accomplish this by using:
In this example, the first tag creates the reference with id footnote_id. The second tag recalls the reference with id footnote_id.

However, this does not work properly under vBulletin. It seems the second form is being removed from the page output because the tag value is empty. In XenForo, this works as expected.

Fixed in the next release.