Bug 135465 [smoke]An error occurred when new a casading Parameter
Description: An error occurred when new a casading Parameter Step to reproduce: 1.new a sample db data source and data set 2.New a cascading parameter group, named "gp1", 3.select the data set, then create two cascading parameters, one is row["customernumber"], named p1; the other is row["customername"] Actual result; error message occurred repeatly
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/CascadingParametersDialog.java
dataSet = inputParameterGroup.getDataSet( );
		if ( dataSet != null )
		{
			dataSetsCombo.setText( "" + dataSet.getName( ) ); 
		}
		else
		{
			dataSetsCombo.select( 0 );
			dataSet = getDataSet( dataSetsCombo.getText( ) );
		}
		cascadingNameEditor.setText( inputParameterGroup.getName( ) );
		valueTable.setInput( inputParameterGroup );
		refreshParameterProperties( );
		updateButtons( );
		return true;
	}
	
	protected void okPressed( )
	{
		try
		{
			saveParameterProperties( );
			inputParameterGroup.setName( cascadingNameEditor.getText( ) );
			inputParameterGroup.setDataSet( dataSet );
		}
		catch ( SemanticException e )
		{
			ExceptionHandler.handle( e );
			refreshParameterProperties( );
			return;