DMS sign_event owner after scheduled msg cleared

[DougLau]

The sign_event table has a msg_owner column, which contains the "owner" of a sign message when activated. After a scheduled message is cleared, the user msg (msg_user) will be activated, with msg_owner set to the user who created that message. This can be confusing if the message is "blank" -- it seems like the user initiated the sign to blank, but in fact, it was just a regular scheduled message expiring with no user interaction.

The fix is to not store blank messages in DMS msg_user