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
ElementPropertyDefn propDefn = element.getPropertyDefn( propName );
		if ( propDefn == null )
			return null;
		if ( propDefn.isUserProperty( ) )
		{
			return new UserPropertyDefnHandle( this,
					(UserPropertyDefn) propDefn );
		}
		return null;
	}
	/**
	 * Returns a list of user properties defined in this element and somewhere
	 * up the inheritance chain. Each object in the list is instance of
	 * <code>UserPropertyDefn</code>.
	 * 
	 * @return The list of user property definitions
	 */
	public List getUserProperties( )
	{
		return getElement( ).getUserProperties( );
	}
	/**
	 * Returns a handle for a top-level property for use in preparing the
	 * Factory data structures. This handle follows specialized rules:
	 * <p>
	 * <ul>
	 * <li>Optimized to get each property value only once.</li>
	 * <li>Indicates if the value is a style property.</li>
	 * <li>Indicates if a style property is set on the element's private style
	 * or a shared style.</li>