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/api/DesignElementHandle.java
* <li>Performs property conversions as needed for the Factory context.
	 * </li>
	 * </ul>
	 * 
	 * @param propName
	 *            the name of the property to get
	 * @return the factory property handle, or <code>null</code> if either 1)
	 *         no property exists with the given name or 2) the property is a
	 *         style property and is not set in a private style.
	 */
	public FactoryPropertyHandle getFactoryPropertyHandle( String propName )
	{
		DesignElement element = getElement( );
		ElementPropertyDefn propDefn = element.getPropertyDefn( propName );
		if ( propDefn == null )
			return null;
		FactoryPropertyHandle handle = new FactoryPropertyHandle( this,
				propDefn );
		if ( handle.isSet( ) )
			return handle;
		return null;
	}
	/**
	 * Returns a handle to the element that contains this element. Every element
	 * except the report design has a container. The container of a parameter,
	 * shared style, data source or data set is the report design itself. The
	 * container of a report item is the section or other report item in which
	 * it appears.
	 * 
	 * @return a handle to the container element.