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
* 
	 * @param d
	 *            A previously defined Date instance
	 */
	public CDateTime( Date d )
	{
		super( );
		setTime( d );
	}
	/**
	 * A constructor that creates an instance from a given <code>Calendar</code>
	 * value
	 * 
	 * @param c
	 *            A previously defined Calendar instance
	 */
	public CDateTime( Calendar c )
	{
		super( );
		setTime( c.getTime( ) );
	}
	/**
	 * A constructor that creates an instance from a given <code>long</code>
	 * value
	 * 
	 * @param lTimeInMillis
	 *            The time defined in milliseconds
	 */
	public CDateTime( long lTimeInMillis )
	{