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
else if ( iUnit == Calendar.MINUTE )
		{
			return "HH:mm:ss"; 
		}
		else if ( iUnit == Calendar.SECOND )
		{
			return "HH:mm:ss"; 
		}
		return null;
	}
	/**
	 * Computes the difference between two given datetime values as a fraction
	 * for the requested field.
	 * 
	 * @param cdt1
	 *            The first datetime value
	 * @param cdt2
	 *            The second datetime value
	 * @param iUnit
	 *            The field with respect to which the difference is being
	 *            computed as a fraction
	 * 
	 * @return The fractional difference between the two specified datetime
	 *         values
	 */
	public static final double computeDifference( CDateTime cdt1,
			CDateTime cdt2, int iUnit )
	{
		return computeDifference( cdt1, cdt2, iUnit, false );
	}