URL:
https://github.com/SSSD/sssd/pull/232
Title: #232: sbus: check connection for NULL before unregister it
pbrezina commented:
"""
We should also set `dbus.conn` to `NULL` on places where we call `dbus_connection_close`
or `dbus_connection_unref`.
"""
See the full comment at
https://github.com/SSSD/sssd/pull/232#issuecomment-293519151