MessageBar calling 'onSendMessage' twice and getting a console error

If my `onSendMessage` function is a react callback, it ends up being called twice when the user adds a message. Also seeing:
```
Cannot update a component (`ChatModelEval`) while rendering a different component (`MessageBar`). To locate the bad setState() call inside `MessageBar`, follow the stack trace as described in https://react.dev/link/setstate-in-render
```
in the console window.