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 dDays / 30.4375;
			}
		}
		else if ( iUnit == Calendar.YEAR )
		{
			if ( trimBelow )
			{
				return cdt1.getYear( ) - cdt2.getYear( );
			}
			else
			{
				
				final double dDays = computeDifference( cdt1,
						cdt2,
						Calendar.DATE );
				return dDays / 365.25;
			}
		}
		return 0;
	}
	/**
	 * Walks through all values in a dataset and computes the least significant
	 * unit for which a difference was noted.
	 * 
	 * @param dsi
	 *            The dataset iterator that facilitates visiting individual
	 *            values
	 * 
	 * @return The least significant unit for which a difference in datetime
	 *         values was noted