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
* Returns the mask of the given property. If the mask of one property has
	 * not been found, looks for its parent or any ancestor.
	 * <p>
	 * Note that this method is only for internal usage. DO NOT call this method
	 * outside the org.eclipse.birt.report.model package.
	 * 
	 * @param module
	 *            the module
	 * @param propName
	 *            the name of the property
	 * 
	 * @return the mask of the given property
	 */
	public String getPropertyMask( Module module, String propName )
	{
		DesignElement e = this;
		do
		{
			ArrayList masks = (ArrayList) e.getLocalProperty( module,
					DesignElement.PROPERTY_MASKS_PROP );
			if ( masks != null )
			{
				for ( int i = 0; i < masks.size( ); i++ )
				{
					PropertyMask mask = (PropertyMask) masks.get( i );
					if ( propName.equals( mask.getName( ) ) )
						return mask.getMask( );
				}
			}
			e = e.getExtendsElement( );