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/api/DesignElementHandle.java
/**
	 * API slot handle array for all slots of this element.
	 */
	private SlotHandle[] slotHandles = null;
	/**
	 * Constructs a handle with the given module.
	 * 
	 * @param module
	 *            the module
	 */
	public DesignElementHandle( Module module )
	{
		this.module = module;
	}
	/**
	 * Returns the report design only when the module is report design.
	 * Otherwise, null is returned. So this method can also be used to check
	 * whether this element is in report design or library.
	 * 
	 * @return the report design, or null if the module is not report design.
	 * @deprecated replaced by getModule()
	 */
	public ReportDesign getDesign( )
	{
		if ( module instanceof ReportDesign )
			return (ReportDesign) module;
		return null;
	}
	/**
	 * Returns the module on which this handle is attached. The returned module