QBluetoothDeviceDiscoveryAgent crash if turn on/off bluetooth fast

I'm working on the project base on example lowenergyscanner.
Step to reproduce:

1. Turn on bluetooth
2. Run the app. it will init QBluetoothDeviceDiscoveryAgent and start discover
3. Turn off bluetooth while is scanning (after app runs 5s)
4. QBluetoothDeviceDiscoveryAgent log error and app crash after 20 -30s

if turn off bluetooth after about 1 minute, don't get the error and app does not crash.