Obdev has just released a new version of LaunchBar that supports Mojave, so use it instead of my theme.
Mojave LaunchBar theme
This is a theme for LaunchBar 6 based on the Default one, and it fixes this:
Here's what it looks like:
Much better, isn't it?
To add this theme to your LaunchBar, simply download the latest release for this repo, unzip it,
then simply double click the
Mojave.lbtheme file and LaunchBar will automatically installs it.
This is just a temporary fix to the Default theme, waiting for Obdev to fix it.