Bug 152430 Key can modify to empty string
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/PropertyCommand.java
stack.execute( propRecord );
		}
		SimplePropertyListRecord record = new SimplePropertyListRecord(
				element, prop, list, value, list.size( ) );
		stack.execute( record );
		if ( value instanceof ElementRefValue )
		{
			ElementRefValue refValue = (ElementRefValue) value;
			if ( refValue.isResolved( ) )
			{
				ElementRefRecord refRecord = new ElementRefRecord( element,
						refValue.getTargetElement( ), prop.getName( ), true );
				stack.execute( refRecord );
			}
		}
		stack.commit( );
	}
	/**
	 * Check to see whether the reference points to a list.
	 * 
	 * @param prop
	 *            the property definition to check whether it is list type
	 * @throws PropertyValueException
	 *             if the property definition is not a list type
	 */
	private void checkListProperty( ElementPropertyDefn prop )
			throws PropertyValueException
	{
		if ( prop.getTypeCode( ) != PropertyType.LIST_TYPE )
			throw new PropertyValueException( element, prop, null,