LSNBLDR-196; prevent adding comment to wrong item


git-svn-id: https://source.sakaiproject.org/svn/lessonbuilder/trunk@118922 66ffb92e-73f9-0310-93c1-f5514f145a0a
LSNBLDR-196; more validity checks for add comment


git-svn-id: https://source.sakaiproject.org/svn/lessonbuilder/trunk@118926 66ffb92e-73f9-0310-93c1-f5514f145a0a