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
* @return the value of the requested property
	 */
	protected Object getIntrinsicProperty( String propName )
	{
		if ( NAME_PROP.equals( propName ) )
			return name;
		if ( EXTENDS_PROP.equals( propName ) )
			return extendsRef;
		assert false;
		return null;
	}
	/**
	 * Sets the value of an intrinsic property. This should be called only from
	 * a command or the design parser. The property name must be valid, and the
	 * value must be valid for that property.
	 * <p>
	 * This class has two intrinsic properties:
	 * <ul>
	 * <li><strong>name </strong>-- The element name. The property value must
	 * be null or a String.
	 * <li><strong>extends </strong>-- The element that this element extends.
	 * Must be a String (for an unresolved name), DesignElement (for a resolved
	 * name) or null. The caller should ensure canExtend of this element is
	 * true.
	 * </ul>
	 * 
	 * @param propName
	 *            The name of the intrinsic property.
	 * @param value
	 *            The value to set for the property.