Bug 202254 Exception is thrown when category values are null and type of X axis is set to DateTime
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/util/CDateTime.java
return Calendar.YEAR;
	}
	/**
	 * Returns the number of days for a particular (month,year) combination
	 * 
	 * @param iMonth
	 *            The month (0-11) for which the day count is to be retrieved
	 * @param iYear
	 *            The year for which the day count is to be retrieved
	 * @return
	 */
	public static final int getMaximumDaysIn( int iMonth, int iYear )
	{
		CDateTime cdt = new CDateTime( );
		cdt.set( Calendar.YEAR, iYear );
		cdt.set( Calendar.MONTH, iMonth );
		return cdt.getActualMaximum( Calendar.DATE );
	}
	/**
	 * Returns the number of days for a particular year
	 * 
	 * @param iYear
	 *            The year for which the day count is to be retrieved
	 * 
	 * @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 );