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
*/
	public DesignElement getReferenceProperty( Module module, String propName )
	{
		ElementRefValue ref = (ElementRefValue) getProperty( module, propName );
		if ( ref == null )
			return null;
		return ref.getElement( );
	}
	/**
	 * Returns whether this element has references. That is, whether any other
	 * elements reference this one using an element reference property. This
	 * query does not check for "extends" references.
	 * 
	 * @return whether other elements refer to this one
	 */
	public boolean hasReferences( )
	{
		return false;
	}
	/**
	 * Creates the Factory data structures for specialized property access. This
	 * method uses specialized property resolution rules:
	 * <p>
	 * <ul>
	 * <li>A property value is either a style property or a non-style property.
	 * </li>
	 * <li>A non-style property is set if this element, or any of its ancestor
	 * elements, provide a value. It is also considered set if the system
	 * provides a default value.</li>
	 * <li>A property value is considered set only if it is set in the private