Do not erase the full account config if an old version of the client stored the password
Do not erase the username and password from the config if we never connected

If we never fetched the credidentials, the _user and _password will be empty,
we should therefore not try to save them because it would just erase them.

Version 1.5.2 always try to fetch the creds at startup.  But now we only
do it if we detect an internet connection