main_window: fix crash due to incorrect logging
this is leftoverof the removal of the logging_manager. rather than self.logging we only need to do logging. this line would otherwise crash passwordsafe if there was no prevously opened safe.
Credits to @deathwhish for spotting.
Fixes: https://gitlab.gnome.org/World/PasswordSafe/-/merge_requests/115
Edited by David Heidelberg