Return an empty dict if no search_order in ldap ext_pillar config file
Return an empty dict if no search_order in ldap ext_pillar config file

I forgot to do this in https://github.com/saltstack/salt/pull/47334, it
is needed to prevent a `KeyError` in these cases.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt