+1 to adamcodega
I got this too after I upgraded to 10.14.
Opened a ticket and it was caused by Restricted Software - I was restricting Facetime, Siri and Mojave.app - disabled the restrictions and box went away immediately. My best guess is that it was Siri but I was so happy to see the box go away didn't troubleshoot further to see specifically which one.
Ok, so, is this like a new product issue in 10.14 maybe? I don't see why the behavior from previous would have intentionally changed to work like this now. If a message isn't configured, it should show no message. Because a message pop up with no text is an infinitely worse user experience than just having an app close for example with no message. At least in my opinion.
Also, some Restricted Software is just configured to alert and not actually close or quit the apps. Even if it that's not it's intended purpose, I know some folks use it that way.
So what gives here? For the record I don't have any Restricted Software items configured so I have not seen this myself, but I'm curious to know what's up with this. Can anyone confirm if this is some kind of defect, or is this new intended behavior?
They will typically list fixed PIs in the release notes: https://docs.jamf.com/10.15.0/jamf-pro/release-notes/Bug_Fixes_and_Enhancements.html
Release notes show that it was:
[PI-007275] Fixed an issue that caused Restricted Software to display a blank error message to users when an error message was not configured.