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
assert prop != null;
		return prop.canInherit( );
	}
	/**
	 * Gets a property value given its definition. This version does the
	 * property search as defined by the given derived component. That is, it
	 * gets the "effective" property value. The definition can be for a system
	 * or user-defined property.
	 * <p>
	 * The search won't search up the containment hierarchy. Meanwhile, it won't
	 * the inheritance hierarchy if the non-style property is not inheritable.
	 * <p>
	 * Part of: Property value system.
	 * 
	 * @param module
	 *            the module
	 * @param prop
	 *            definition of the property to get
	 * @return The property value, or null if no value is set.
	 */
	public Object getPropertyFromElement( Module module,
			ElementPropertyDefn prop )
	{
		Object value = null;
		value = getPropertyFromSelf( module, prop );
		if ( value != null )
			return value;