Crash when discovery Bluetooth LE device on Windows with Bluetooth off

seem, when i tried discovery BT devices with BT off, it crashed.
but, i don't know how to know BT driver on or off. do QT lib support this?
QBluetoothLocalDevice::hostModeStateChanged() and HostMode hostMode() always has result: QBluetoothLocalDevice::HostConnectable . -> it doesn't work well?

ASSERT failure in void __cdecl QWinRTBluetoothDeviceDiscoveryWorker::setupLEDeviceWatcher(void): "The device is not ready for use.", file qbluetoothdevicediscoveryagent_winrt.cpp, line 414

OS: windows 10 (almost newest version){{}}
QT: 5.15.2.
Happened every time.