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
	 *            The name of the property to set. Must be valid. Can be a
	 *            system-defined or user-defined property name.
	 * @param value
	 *            The value to set. Must be valid for the property.
	 */
	public void setProperty( String propName, Object value )
	{
		ElementPropertyDefn prop = getPropertyDefn( propName );
		
		
		assert prop != null;
		setProperty( prop, value );
	}
	/**
	 * Sets the value of a property. The value must have already been validated,
	 * and must be of the correct type for the property. The property must be
	 * valid for this object. The property can be a system or user-defined
	 * property. The value is set locally. If the value is null, then the
	 * property is "unset."
	 * <p>
	 * Part of: Property value system.
	 * 
	 * @param prop
	 *            The property definition. Must be valid. Can be a
	 *            system-defined or user-defined property.
	 * @param value
	 *            The value to set. Must be valid for the property.
	 */
	public void setProperty( ElementPropertyDefn prop, Object value )