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
* operations that change an element <strong>must </strong> be made though a
 * command. So, if you find a method <code>setMumble( )</code> that is of
 * interest, you must locate (or create) a <code>SetMumble</code> command to
 * perform this operation in a way that can be undone. Also, some of the
 * operations described here are incomplete, in that they handle a task only on
 * this one element. Many tasks must be done on several elements to be complete.
 * For example, if we call the <code>setExtends( )</code> method of element E,
 * we also must cache the inverse relationships in the parent element. This
 * higher-level semantic processing is handled by code above this class.
 * 
 * <h3>Meta-data</h3>
 * 
 * This class stores information that the user enters for a design element.
 * Every element is defined by an <em>element definition </em>. The
 * relationship between an element and element definition is much like that
 * between a object and a class in Java. The element definition defines
 * characteristics of the element, and is fixed by the development team. The
 * element is defined by the user and contains information needed for a
 * particular report.
 * <p>
 * The {@link #getDefn}method provides access to the element definition for the
 * particular element. The returned {@link ElementDefn}object provides access
 * to the properties defined for the element as well as other information.
 * <p>
 * This abstract base class provides operations common to all (or most)
 * elements. The application creates Java subclasses to represent the various
 * kinds of report elements. Those subclasses provide the behavior specific to
 * that element type, usually allocating space for any element slots and
 * providing a callback into the {@link ElementVisitor design visitor}class.
 * <p>