Null Alt Text in PDF

Has anyone else noticed the appearance of null alt text on LINK tags in PDFs exported from Indesign since the upgrade?  If so, do you know how to prevent it?  This is an accessibility issue.   The question is, is it a BUG or something designers are doing that causes this?

Null alt text is not the same thing as "no alt text."  Null alt text in a PDF prevents the contents of a tag from being read by the screen reader.  Here is what it looks like in the Tags Properties under Tag Element.  The contents of this tag, whatever they are, will not be read by the screen reader.  In this case it's a Link tag.

Here is what no alt or actual text would look like on an empty <P> tag.