Thank you for alerting us!
I was not completely surprised, though. The base theme (on which all other themes build) carries a heavy technological debt, being more than 10 years old. I've done a bit of cleaning, but it appears I neglected some moving parts.
I lost patience with the base theme and I started a complete rehaul of the 'Modern' theme's CSS, which should be ready much faster than the new theme I teased Modman about a long time ago. So, until the rehaul completes, I applied a local patch to fix this particular issue.
Forum Maintenance & Development News/Announcements
Have a look here for general information about the forum, rules and announcements.