Image hotspots using map tag results in error message

[Ben]

Version 6.29.0
64 bit Windows 10 Home

When I use image hotspots using, for example:

<img src="../resources/images/image.png" usemap="#workmap"/>
<map name="workmap">
  <area shape="circle" coords="114,18,50" alt="Terms and acronyms"
    href="../general/terms_and_acronyms.html"/>
</map>

... Calibre produces this link when I hover over the hotspot:

clbr://internal.sandbox/books/terms_and_acronyms.xhtml

Note the ".xhtml" extension in the link. My files are .html files built as an ebook (.epub) using XMLMind Compiler (ebookc) (not sure if the .xhtml extension is the cause but may be relevant).

When I click the link, a blank page is opened and the banner message displays:
"This page contains the following errors:
error on line 1 at column 1: Document is empty
Below is a rendering of the page up to the first error."

If I open another page, Calibre indicates "Loading next section " and does not load the page (the circle renders continuously). I have to close Calibre and re-open the application to be able to read the book.

I tested in VitalSource Bookshelf (another ebook reader) and the link works fine, so this issue is specific to Calibre.

I have attached the book. Click on the "Equation" hotspot on the image in the "Organisation structure - Teams perspective" topic.

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.