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/model/data/util/DataSwitch.java
* @param object the target of the switch.
	 * @return the result of interpretting the object as an instance of '<em>Bubble Data Set</em>'.
	 * @see #doSwitch(org.eclipse.emf.ecore.EObject) doSwitch(EObject)
	 * @generated
	 */
	public Object caseBubbleDataSet( BubbleDataSet object )
	{
		return null;
	}
	/**
	 * Returns the result of interpretting the object as an instance of '<em>Element</em>'.
	 * <!-- begin-user-doc -->
	 * This implementation returns null; returning a non-null result will terminate the switch. <!-- end-user-doc -->
	 * @param object the target of the switch.
	 * @return the result of interpretting the object as an instance of '<em>Element</em>'.
	 * @see #doSwitch(org.eclipse.emf.ecore.EObject) doSwitch(EObject)
	 * @generated
	 */
	public Object caseDataElement( DataElement object )
	{
		return null;
	}
	/**
	 * Returns the result of interpretting the object as an instance of '<em>Set</em>'.
	 * <!-- begin-user-doc --> This
	 * implementation returns null; returning a non-null result will terminate the switch. <!-- end-user-doc -->
	 * @param object the target of the switch.
	 * @return the result of interpretting the object as an instance of '<em>Set</em>'.
	 * @see #doSwitch(org.eclipse.emf.ecore.EObject) doSwitch(EObject)
	 * @generated