dev: added log messages, add null check

git-svn-id: http://notifications-widget.googlecode.com/svn/trunk@411 21922344-3934-ee51-d6e3-fd981ce84c01
bugfix: all notifications are cleared when a single notification is cleared

git-svn-id: http://notifications-widget.googlecode.com/svn/trunk@412 21922344-3934-ee51-d6e3-fd981ce84c01