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
return MILLIS_IN_HOUR;
		}
		else if ( iUnit == Calendar.DATE )
		{
			return MILLIS_IN_DAY;
		}
		else if ( iUnit == Calendar.MONTH )
		{
			return MILLIS_IN_DAY * 30.4375;
		}
		else if ( iUnit == Calendar.YEAR )
		{
			return MILLIS_IN_DAY * 365.25;
		}
		return 0;
	}
	/**
	 * Zeroes out all units for this datetime instance below a specified unit.
	 * 
	 * @param iUnit
	 *            The unit below which all values are to be zeroed out
	 */
	public final void clearBelow( int iUnit )
	{
		if ( iUnit == YEAR )
		{
			set( Calendar.MILLISECOND, 0 );
			set( Calendar.SECOND, 0 );
			set( Calendar.MINUTE, 0 );
			set( Calendar.HOUR, 0 );