Yeah, don't worry about it it shouldn't cause any harm to your peeps.
That minor bug has been reported many times, although it's completely harmless and avoidable. It only occurs when you praise a peep, by any of the various means, for reading email. Since it doesn't cause any problems with the game, it can be safely ignored.
There are lots of topics about this error, next time you can try doing a quick search to see if anyone has talked about it before
I'll put some of them here for future reference:
A bug!!!Unknown String Id in virtual familiesanyone else seen this?
Previous Topic
Index
