Bug 152430 Key can modify to empty string
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/PropertyCommand.java
copy );
			getActivityStack( ).execute( propRecord );
		}
		return;
	}
	/**
	 * Check to see whether the reference points to a list.
	 * 
	 * @param ref
	 *            reference to the list into which to add the structure
	 * @throws PropertyValueException
	 *             if the <code>ref</code> doesn't refer a list property or
	 *             member.
	 */
	private void checkListMemberRef( MemberRef ref )
			throws PropertyValueException
	{
		if ( !ref.isListRef( ) )
			throw new PropertyValueException( element, ref.getPropDefn( ),
					null, PropertyValueException.DESIGN_EXCEPTION_NOT_LIST_TYPE );
	}
	/**
	 * Validates the values of the item members.
	 * 
	 * @param ref
	 *            reference to a list.
	 * @param item
	 *            the item to check
	 * @throws SemanticException
	 *             if the item has any member with invalid value or if the given