When I launch the messages app on my iMac I get a notice that the Messages database is being upgraded. The notice, shown below, tells me to wait while it finishes or relaunch later. This just started recently and has been going on for 2 days now. Any idea how to check my messages? I'm running High Sierra and have been for a while now so this doesn't appear tied to the system upgrade. I've tried quitting and returning several times and also tried just leaving notice up. Neither attempt worked.