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
* @param propName
	 *            name of the property to get. Can be a system-defined or
	 *            user-defined property name. Must be of the correct case.
	 * @return The property value, or null if no value is set.
	 */
	public Object getProperty( Module module, String propName )
	{
		ElementPropertyDefn prop = getPropertyDefn( propName );
		
		if ( prop == null )
			return null;
		return getProperty( module, prop );
	}
	/**
	 * Returns the property value from this element's parent, or its virtual
	 * parent. The value is only from local properties, or local style of its
	 * ancestor.
	 * 
	 * @param module
	 *            module
	 * @param prop
	 *            definition of the property to get.
	 * @return property value, or <code>null</code> if no value is set.
	 */
	protected Object getPropertyFromParent( Module module,
			ElementPropertyDefn prop )
	{
		Object value = null;
		DesignElement e = this;
		do