I finally decided to upgrade to Big Sur. Getting "null" set and error. I'm in Mojave. Do I need to go to Catalina first? I don't want Monterey yet. I just got comfortable with Big Sur. I'm upgrading (supposedly) from the System Preferences. FYI: When I first clicked on the "upgrade to Big Sur" and it went to Monterey. I went back, started again and since then can't get there from here.