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
}
	}
	/**
	 * Returns a preferred format specifier for tick labels that represent axis
	 * values that will be computed based on the difference between cdt1 and
	 * cdt2
	 * 
	 * @param iUnit
	 *            The unit for which a preferred pattern is being requested
	 * 
	 * @return A preferred datetime format pattern for the given unit
	 */
	public static final String getPreferredFormat( int iUnit )
	{
		if ( iUnit == Calendar.YEAR )
		{
			return "yyyy"; 
		}
		else if ( iUnit == Calendar.MONTH )
		{
			return "MMM yyyy"; 
		}
		else if ( iUnit == Calendar.DATE )
		{
			return "MM-dd-yyyy"; 
		}
		else if ( iUnit == Calendar.HOUR_OF_DAY )
		{
			return "MM-dd-yy\nHH:mm"; 
		}