app crashes when flutterBluePlus startScan called

I have an application that connects to to Bluetooth device. I used the code from the following example:

Creating an App for Interacting with IoT Devices using BLE and FlutterFlow

I had the scan working, and then went to work on other portion of the app display the data. When I went back to complete the connection the app crashes.

final flutterBlue = FlutterBluePlus.instance;

I traced the cause down to the following code:

await flutterBlue.startScan( timeout: const Duration(seconds: 5), );