Bug 161219 Gantt chart with null datapoints fail to render
Create a dataset with two date columns, having some null date values Create a gantt chart Assign the dates to the gant series It fails to render and throw exception. Expected: null dates should be treated as: - 1 null date, 1 valid date ->one marker drawn, no line - 2 null dates -> skip rendering of datapoint If the decoration label is missing it should also not fail.
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/util/CDateTime.java
*/
	public static final int getDifference( CDateTime cdt1, CDateTime cdt2 )
	{
		if ( cdt1.getYear( ) != cdt2.getYear( ) )
		{
			return Calendar.YEAR;
		}
		else if ( cdt1.getMonth( ) != cdt2.getMonth( ) )
		{
			return Calendar.MONTH;
		}
		else if ( cdt1.getDay( ) != cdt2.getDay( ) )
		{
			return Calendar.DATE;
		}
		else if ( cdt1.getHour( ) != cdt2.getHour( ) )
		{
			return Calendar.HOUR_OF_DAY;
		}
		else if ( cdt1.getMinute( ) != cdt2.getMinute( ) )
		{
			return Calendar.MINUTE;
		}
		else if ( cdt1.getSecond( ) != cdt2.getSecond( ) )
		{
			return Calendar.SECOND;
		}
		else
		{
			return 0;