Bug 124620 Referenced Parameter icon should be invalid if the parameter in library is deleted
Description: Referenced parameter icon should be invalid if the source parameter in library is deleted. Steps to reproduce: 1.Create a library. Insert a report scalar parameter. 2.Create a report, use the above library. In the library explorer, pull the parameter to the data explorer view of report. 3.Open the library file, delete the parameter. Then reopen the report design file, the icon of parameter seems nothing happened. But if those operations happened in dataset, the icon of dataset in the report will be invalid. It is acceptable. Expected Result: The icon of referenced parameter should be invalid.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
/**
	 * Returns the property value which is related to slot selector. It is from
	 * the selector style which represents the slot or combination of container
	 * and slot.
	 * 
	 * @param module
	 *            the module
	 * @param prop
	 *            the definition of property
	 * @return the property value, or null if no value is set.
	 */
	protected Object getPropertyFromSlotSelector( Module module,
			ElementPropertyDefn prop )
	{
		if ( getContainer( ) == null )
			return null;
		String selector = getContainer( ).getSelector( getContainerSlot( ) );
		return getPropertyFromSelector( module, prop, selector );
	}
	/**
	 * Returns the property value which is related to container.
	 * 
	 * @param module
	 *            the module
	 * @param prop
	 *            the definition of property
	 * @return the property value, or null if no value is set.
	 */
	protected Object getPropertyRelatedToContainer( Module module,
			ElementPropertyDefn prop )