Open Medici desktop client and select "Add Tag" from the Metadata Page view, it says "Adding a Tag to 1 Dataset" when nothing is selected and when you enter a tag and click "OK", the following error is reported:

!MESSAGE An internal error occurred during: "Adding tags".
!STACK 0
java.lang.IllegalArgumentException: unable to convert object null to RDF
at org.tupeloproject.rdf.ObjectVisitor.visit(ObjectVisitor.java:79)
at org.tupeloproject.rdf.Triple.create(Triple.java:80)
at org.tupeloproject.rdf.Triple.create(Triple.java:96)
at org.tupeloproject.kernel.Context.addTriple(Context.java:337)
at edu.uiuc.ncsa.cet.bean.tupelo.AssociatableTupeloBeanUtil.addAssociationTo(AssociatableTupeloBeanUtil.java:111)
at edu.illinois.ncsa.mmdb.desktop.ui.handlers.AddTagHandler.addTagToSubject(AddTagHandler.java:118)
at edu.illinois.ncsa.mmdb.desktop.ui.handlers.AddTagHandler.tagSubject(AddTagHandler.java:82)
at edu.illinois.ncsa.mmdb.desktop.ui.handlers.AddTagHandler$1.run(AddTagHandler.java:57)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)