Bug 202891 NPE throws out when click on data item in layout[0001]
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/dialogs/BindingDialogHelper.java
ExpressionBuilder expression = new ExpressionBuilder( combo.getText( ) );
				expression.setExpressionProvier( expressionProvider );
				if ( expression.open( ) == Window.OK )
				{
					if ( expression.getResult( ) != null )
						combo.setText( expression.getResult( ) );
				}
			}
		} );
		if ( isRef )
		{
			expressionButton.setEnabled( false );
		}
	}
	protected void setExpressionButtonImage( Button button )
	{
		String imageName;
		if ( button.isEnabled( ) )
		{
			imageName = IReportGraphicConstants.ICON_ENABLE_EXPRESSION_BUILDERS;
		}
		else
		{
			imageName = IReportGraphicConstants.ICON_DISABLE_EXPRESSION_BUILDERS;
		}
		Image image = ReportPlatformUIImages.getImage( imageName );
		GridData gd = new GridData( );
		gd.widthHint = 20;
		gd.heightHint = 20;
		button.setLayoutData( gd );