Error when selecting Categories

[humdinger]

Originally filed at https://dev.haiku-os.org/ticket/15166 by luroh:

To repeat:

• Go to ​https://depot.haiku-os.org
• Select 'Categories'

Result: Oh darn! Something has gone wrong with your use of this web application.

This is a screenshot of WebPositive's script console (no copy&paste of text in there...):
http://ix.io/1OIk