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
* User-defined elements can extend other elements, but style element is not
 * allowed to extend each other. The following is the terminology used for this
 * system.
 * <ul>
 * <li>If element E extends element D, then D is said to be the
 * <em>parent </em> element, and element E is the <em>derived </em> element.
 * </li>
 * <li>We can also use the term <em>base </em> as a synonym for parent. That
 * is, D is the base element above.</li>
 * <li>Element D may in turn extend another element C.</li>
 * <li>We say that C and D are <em>ancestor </em> elements of E, and that D
 * and E are <em>descendents </em> of C.</li>
 * <li>In this simple hierarchy, element E is the <em>most derived </em>
 * element, while element C is the <em>most base </em> element.</li>
 * </ul>
 * <p>
 * Inheritance applies to the following:
 * <p>
 * <dl>
 * <dt><strong>Property values </strong></dt>
 * <dd>An element inherits any property values defined by any of its ancestors.
 * If two ancestors define values for the same property, then the inherited
 * value is that defined by the most derived ancestor. This rule is similar to
 * the method overriding rules in Java.</dd>
 * 
 * <dt><strong>Named style </strong></dt>
 * <dd>If an ancestor element explicitly names a style, then the derived
 * element will also use that style (unless the derived element specifies a
 * different style.)</dd>
 *