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
* {@link Module#getElementByID}to obtain and element given an element ID.
 * </dd>
 * </dl>
 * 
 * <h3>Element Visitor</h3>
 * 
 * A visitor class is a design pattern that is useful for implementing certain
 * kinds of algorithms that need to "touch" many different elements. One could
 * code the element by adding methods to each element, but doing so is
 * cumbersome, complex, and error-prone. Better is to define a <em>visitor</em>
 * class that has methods for each element. One simply <em>applies</em> the
 * visitor to an element, and the element then calls its specific "visit" method
 * in the visitor. For example, the design engine uses a visitor to write the
 * design to an XML file.
 * 
 * <h3>API Handles</h3>
 * 
 * This class, and its subclasses, are low-level classes that maintain the state
 * of the design. Property and slot methods are generic so that they work for
 * all elements. Modifications must be done through commands. The application,
 * however, wants to work with a simpler set of objects, and wants to work with
 * specific "getter" methods to get properties. The application also simply
 * wants to call a "setter" method to make a change.
 * <p>
 * The API handle package provides a set of "facade" classes that give this
 * high-level view. Therefore, the application will seldom work with this class
 * directly. Instead, it will work with the handle produced by calling the
 * {@link #getHandle( Module module )}method.
 * 
 * <h3>Semantic State</h3>