posts_nav_link always outputs link

[orangenormal]

posts_nav_link will always echo a link tag, even when the beginning/end of the posts have been reached. The link text, however, is omitted, leaving an empty link (i.e.: <a href="​http://example.com/page/2/"></a>) in the HTML output.

In addition to cluttering the output, this has consequences if one is testing the PHP output buffer for writing container tags for the link.