At this point, though, if you are using the package in a .LRN environment you should not upgrade as Malte's diagnosis is correct. Unfortunately, the portlet depends on a piece of the data model which no longer serves a purpose in the package and in fact is detrimental to its progress. I think that the best course of action at this point is to fix the portlet so that it works in a sensible way does not hamstring further development of the package. Since releasing another version of the package with Malte's comment in the upgrade script would cause data model inconsistencies, I have removed it with the hope that interested parties can collaborate on a fix for the portlet.
Moving forward, if there are any users or developers who would like to work with me to ensure that the portlet continues to function, that would be great.