Replaced these functions with the following:
    def get_string_list(self,column):
        """Return a column as a QStringList"""
        tempList = QStringList()
        result = QtSql.QSqlQuery('''SELECT %s FROM presentations''' %column)
        while result.next():
            tempList.append(result.value(0).toString())
        tempList.removeDuplicates()
        return tempList