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 The number of days in the specified year
	 */
	public static final int getMaximumDaysIn( int iYear )
	{
		CDateTime cdt = new CDateTime( );
		cdt.set( Calendar.YEAR, iYear );
		return cdt.getActualMaximum( Calendar.DAY_OF_YEAR );
	}
	/**
	 * A convenience method provided to return the number of milliseconds
	 * available in a given unit
	 * 
	 * @param iUnit
	 *            The unit for which the number of milliseconds are to be
	 *            computed
	 * 
	 * @return The number of milliseconds for the specified unit
	 */
	public static final double inMillis( int iUnit )
	{
		if ( iUnit == Calendar.SECOND )
		{
			return MILLIS_IN_SECOND;
		}
		else if ( iUnit == Calendar.MINUTE )
		{
			return MILLIS_IN_MINUTE;
		}
		else if ( iUnit == Calendar.HOUR )
		{