Bug 317267 [Automation][Regression]Error is thrown out when preview gantt type chart
chart/org.eclipse.birt.chart.engine.extension/src/org/eclipse/birt/chart/extension/datafeed/GanttDataSetProcessorImpl.java
if ( calMin.after( cala[j] ) )
						{
							calMin = cala[j];
						}
					}
					else if ( cala[j] != null )
					{
						calMin = cala[j];
					}
				}
			}
		}
		return calMin;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.chart.datafeed.IDataSetProcessor#getMaximum(org.eclipse.birt.chart.model.data.DataSet)
	 */
	public final Object getMaximum( DataSet ds ) throws ChartException
	{
		DataSetIterator dsi = null;
		try
		{
			dsi = new DataSetIterator( ds );
			dsi.reset( );
		}
		catch ( IllegalArgumentException uiex )
		{
			throw new ChartException( ChartEngineExtensionPlugin.ID,