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
userProperties = new LinkedHashMap( );
		userProperties.put( propName, userProp );
	}
	/**
	 * Drops a user-defined property. The application must have previously
	 * removed all existing values for that property. The application must have
	 * previously validated that the user-defined property does exist, and is
	 * defined on this element.
	 * <p>
	 * Part of: User-defined property system.
	 * 
	 * @param prop
	 *            The user-defined property.
	 */
	public void dropUserPropertyDefn( UserPropertyDefn prop )
	{
		assert getDefn( ).allowsUserProperties( );
		assert userProperties != null;
		assert userProperties.get( prop.getName( ) ) == prop;
		userProperties.remove( prop.getName( ) );
	}
	/**
	 * Gets a user property definition defined on this class itself.
	 * <p>
	 * Part of: User-defined property system.
	 * 
	 * @param propName
	 *            The internal name of the user-defined property.
	 * @return The user-defined property definition, if any.
	 */