if ( selection.length <= 0
if ( selection.length > 0 && selection[0].getData( ) instanceof DbObject ) { if ( ( (DbObject) selection[0].getData( ) ).getType( ) == DbObject.PROCEDURE_TYPE ) { event.doit = false; return; }; } else if ( selection.length <= 0
			public void dragStart( DragSourceEvent event )			{				TreeItem[] selection = availableDbObjectsTree.getSelection( );				if ( selection.length <= 0						|| selection[0].getData( ) == null )				{					event.doit = false;					return;				}			}