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
if ( parent == null )
			return null;
		return parent.getHandle( parent.getRoot() );	
	}
	/**
	 * Sets this element to extend the given element.
	 * 
	 * @param parent
	 *            handle to the element that this element is to extend. If
	 *            <code>null</code>, then this element will no longer extend
	 *            another element.
	 * @throws ExtendsException
	 *             if the parent element is of the wrong type as this element.
	 */
	public void setExtends( DesignElementHandle parent )
			throws ExtendsException
	{
		ExtendsCommand cmd = new ExtendsCommand( module, getElement( ) );
		cmd.setExtendsElement( parent );
	}
	/**
	 * Sets the name of the element that this element extends. The name must
	 * resolve to an element of the same type as this element.
	 * 
	 * @param name
	 *            the name of the element that this one is to extend
	 * @throws ExtendsException
	 *             if no element exists with the given name, or if the element
	 *             is of the wrong type.
	 */