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
CachedMetaDataHandle cmdh = null;
		try
		{
			cmdh = DataSetUIUtil.getCachedMetaDataHandle( dataSet );
		}
		catch ( SemanticException e )
		{
		}
		if ( cmdh != null )
		{
			for ( Iterator iter = cmdh.getResultSet( ).iterator( ); iter.hasNext( ); )
			{
				ResultSetColumnHandle element = (ResultSetColumnHandle) iter.next( );
				if ( value.equalsIgnoreCase( DEUtil.getColumnExpression( element.getColumnName( ) ) ) )
				{
					return element.getColumnName( );
				}
			}
		}
		return null;
	}
	private void updateButtons( )
	{
		boolean okEnable = true;
		if ( dataSet == null )
		{