Bug 151552 Can't change the Data Set of a chart drag from a library
After creating a library with a chart,you use it and drag the chart to a report design.A error happen when you change the Data Set of the chart. 1.creat a library,add a chart into it ,then publish the library. 2.new a report and use the library ,drag the chart into the layout of the report,you can't change the data set of the chart,or a error will occur. Actual result:A error occur when you change the data set] Expected result:You can change the data set.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/PropertySearchStrategy.java
*/
	protected Object getPropertyFromSlotSelector( Module module,
			DesignElement element, ElementPropertyDefn prop )
	{
		if ( element.getContainer( ) == null )
			return null;
		String selector = element.getContainer( ).getSelector(
				element.getContainerSlot( ) );
		return getPropertyFromSelector( module, prop, selector );
	}
	/**
	 * Returns property value with predefined style.
	 * 
	 * @param module
	 *            module
	 * @param prop
	 *            definition of property to get
	 * @param selector
	 *            predefined style
	 * @return The property value, or null if no value is set.
	 */
	protected Object getPropertyFromSelector( Module module,
			ElementPropertyDefn prop, String selector )
	{
		assert module != null;
		if ( selector == null )
			return null;
		
		StyleElement style = module.findStyle( selector );
		if ( style != null )