it seems you have changed something that makes adding text objects requiring a font to be defined.
This causes scripts that has worked for over a year to suddenly fail and is a problem.
I don’t think it’s OK to change stuff like that in a minor SR (nor in a bigger update as going from V6 to V7 either actually) since Rhino is more or less auto updated, and thus this causes issues for those who has scripts that uses text objects with default fonts in production.
Note: rs.AddText() says it has font as OPTIONAL.
So if you want to change something then do it behind the scene adding Arial as default if nothing is defined by the user.