if(getViewer()==null) { return; }
	public void createControl( Composite parent )	{		tree = new Tree( parent, SWT.NONE );		treeCommon.setTree( tree );		treeCommon.setExpressionViewer( getViewer( ) );		treeCommon.createDefaultExpressionTree( SessionHandleAdapter.getInstance( )				.getReportDesignHandle( )				.getVisibleDataSets( ) );		treeCommon.addMouseTrackListener( );		treeCommon.addMouseListener( );		treeCommon.addDragSupportToTree( );		treeCommon.addDropSupportToViewer( );		// Add tool tips		tree.setToolTipText( "" ); //$NON-NLS-1$	}