Do not print line number of it equals to zero. As per [1], it indicates that is is not related to a file content.

[1] http://checkstyle.sourceforge.net/apidocs/com/puppycrawl/tools/checkstyle/api/AuditEvent.html#getLine%28%29

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1563595 13f79535-47bb-0310-9956-ffa450edef68