Bug 121498 When datasource/dataset deleted, the datasource/dataset property binding element haven't been deleted
When deleted the datasource/dataset, the datasource/dataset property binding element haven't been deleted. Expected result: This operation must be a transaction.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/DesignElementHandle.java
return null;
		return new PropertyHandle( this, propDefn );
	}
	/**
	 * Returns a user-defined property handle for a top-level property. A
	 * top-level property is a property that defines on an element.
	 * 
	 * @param propName
	 *            the name of the property to get
	 * @return the user property definition handle, or <code>null</code> if
	 *         the no property exists with the given name or it is not a
	 *         user-defined property.
	 */
	public UserPropertyDefnHandle getUserPropertyDefnHandle( String propName )
	{
		DesignElement element = getElement( );
		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>.