Fix disconnect in the global BlueZ manager

[bdraco]

Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/config_entries.py", line 357, in async_setup
    result = await component.async_setup_entry(hass, self)
  File "/usr/src/homeassistant/homeassistant/components/bluetooth/__init__.py", line 253, in async_setup_entry
    await manager.async_start(
  File "/usr/src/homeassistant/homeassistant/components/bluetooth/__init__.py", line 343, in async_start
    await self.scanner.start()  # type: ignore[no-untyped-call]
  File "/usr/local/lib/python3.10/site-packages/bleak/backends/bluezdbus/scanner.py", line 128, in start
    manager = await get_global_bluez_manager()
  File "/usr/local/lib/python3.10/site-packages/bleak/backends/bluezdbus/manager.py", line 808, in get_global_bluez_manager
    await instance.async_init()
  File "/usr/local/lib/python3.10/site-packages/bleak/backends/bluezdbus/manager.py", line 344, in async_init
    await self._bus.disconnect()
TypeError: object NoneType can't be used in 'await' expression

[bdraco]

Logger: bleak.backends.bluezdbus.client
Source: components/switchbot/cover.py:94
First occurred: 10:36:23 (1 occurrences)
Last logged: 10:36:23
Failed to cancel connection (/org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX): 'NoneType' object has no attribute 'call'

Actually thats a different issue.... and fixed in #919

[dlech]

merged, thanks!