Sorry, I inadvertently let a simple typo slip through in the latest release, 3.3.12.
It doesn’t have any effect on data, or normal editing though. But what it does do is prevent the “Manage media” feature in Administration from working, which can be annoying.
The good news is that the fix is a simple one-file replacement. Just download the zip-folder attached here, and copy the file ‘admin_media.php’ to your server, replacing the existing file of the same name in your kiwitrees root folder.
Recognising the bug is simple. Visit Administration > Media > Manage media. You will see this message:

Now click ‘close’ in that pop-up box, and you will see this:

Not very useful. But once you replace the errant file, all will be back to normal.