Hi Guys,
this already fixed bug took me some time to locate.
To upgrade my installation, I downloaded version 1.4.9 with the download link on the download page (https://github.com/zenphoto/zenphoto/archive/zenphoto-1.4.9.tar.gz) and got the buggy version. Downloading the zenphoto-master.zip worked
As this bug doesn't appear in any theme, only few installations might be affected.
Nevertheless updating the link/package would perserve other ones from struggeling with this issue too.
Regards
Markus