If the user makes an Accurev transaction without a comment, then AccurevTransaction::getMsg() returns NULL. The impact of this is breaking plugins (e.g. email-ext) that rely on it being a non-null value

Per documentation on ChangeLogSet.Entry's getMsg() method, the return value can be empty but never NULL.
http://javadoc.jenkins-ci.org/hudson/scm/ChangeLogSet.Entry.html#getMsg()