* Short circuit EmailNotification::notify() to not call EmailNotification::commonMess...

* Short circuit EmailNotification::notify() to not call EmailNotification::commonMessageKeys() if there're no users to notify. This is a hack to work arround the following exception:
A database query syntax error has occurred.
The last attempted database query was:
"SELECT gu_id, lu_wiki, gu_salt, gu_password,gu_auth_token, gu_locked,gu_hidden,gu_registration,gu_email,gu_email_authenticated FROM `parsertest_globaluser` LEFT OUTER JOIN `parsertest_localuser` ON gu_name=lu_name AND lu_wiki='test2wiki-parsertest_' WHERE gu_name='127.0.0.1'"
from within function "Database::safeQuery".
MySQL returned error "1146: Table 'centralauth.parsertest_globaluser' doesn't exist (127.0.0.1)"
* Whitespaces fixes