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
* Checks all structures in the specific property whose type is structure
	 * list property type. This method is used in command. If any error is
	 * found, the exception will be thrown.
	 * 
	 * @param module
	 *            the module
	 * @param propDefn
	 *            the property definition of the list property
	 * @param list
	 *            the structure list to check
	 * @param toAdd
	 *            the structure to add. This parameter maybe is
	 *            <code>null</code>.
	 * @throws PropertyValueException
	 *             if the structure list or the structure to add has any
	 *             semantic error..
	 */
	public void checkStructureList( Module module, PropertyDefn propDefn,
			List list, IStructure toAdd ) throws PropertyValueException
	{
		List errorList = StructureListValidator.getInstance( )
				.validateForAdding( getHandle( module ), propDefn, list, toAdd );
		if ( errorList.size( ) > 0 )
		{
			throw (PropertyValueException) errorList.get( 0 );
		}
	}
	/**
	 * Checks the parent element.
	 *