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/DataAdapterFactory.java
* <!-- begin-user-doc -->
	 * This default implementation returns null so that we can easily ignore cases;
	 * it's useful to ignore a case when inheritance will catch all the cases anyway.
	 * <!-- end-user-doc -->
	 * @return the new adapter.
	 * @see org.eclipse.birt.chart.model.data.DifferenceDataSet
	 * @generated
	 */
	public Adapter createDifferenceDataSetAdapter( )
	{
		return null;
	}
	/**
	 * Creates a new adapter for an object of class '{@link org.eclipse.birt.chart.model.data.GanttDataSet <em>Gantt Data Set</em>}'.
	 * <!-- begin-user-doc -->
	 * This default implementation returns null so that we can easily ignore cases;
	 * it's useful to ignore a case when inheritance will catch all the cases anyway.
	 * <!-- end-user-doc -->
	 * @return the new adapter.
	 * @see org.eclipse.birt.chart.model.data.GanttDataSet
	 * @generated
	 */
	public Adapter createGanttDataSetAdapter( )
	{
		return null;
	}
	/**
	 * Creates a new adapter for an object of class '{@link org.eclipse.birt.chart.model.data.NumberDataElement <em>Number Data Element</em>}'.
	 * <!-- begin-user-doc
	 * --> This default implementation returns null so that we can easily ignore cases; it's useful to ignore a case