Bug 313297 XML data set fail in chart data preview
chart/org.eclipse.birt.chart.ui/src/org/eclipse/birt/chart/ui/swt/CustomPreviewTable.java
}
	public String getColumnHeading( int iIndex )
			throws IllegalArgumentException
	{
		if ( isDummy )
		{
			return ""; 
		}
		if ( fHeadings == null || iIndex >= fHeadings.size( ) )
		{
			throw new IllegalArgumentException( Messages.getString( "CustomPreviewTable.Exception.InvalidColumnIndexNotDefined", String.valueOf( iIndex ) ) ); 
		}
		return fHeadings.get( iIndex ).getName( );
	}
	/**
	 * Returns the column heading of the column that the user right-clicked on
	 * last. null if user hasn't right-clicked in the table yet. This method is
	 * for use to determine the column for which the popup-menu is to be
	 * displayed...since the menu is handled externally.
	 * 
	 * @return the last column in which the user has right-clicked.
	 */
	public String getCurrentColumnHeading( )
	{
		return ( iColumnIndex != -1 ) ? fHeadings.get( iColumnIndex ).getName( )
				: null;
	}
	/**
	 * Returns head object of current column, if it is sharing query, the head
	 * object should be instance of <code>ColumnBindingInfo</code>, else it is