The wallet is crashing without these new conf lines in place. I wasn't aware that they were needed. I assume the update automatically adds them, but I had another config file corruption from a system crash. I restored from a recent backup but apparently not recent enough.

Adding the testnet node and flag lines to my config allows the wallet to start. There may still be an issue, but I'm waiting to see what happens. Removing the lines from my config reproduces the captured error.