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/impl/DataFactoryImpl.java
return createDataFromString( eDataType, initialValue );
			default :
				throw new IllegalArgumentException( "The datatype '" + eDataType.getName( ) + "' is not a valid classifier" ); 
		}
	}
	/**
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	public String convertToString( EDataType eDataType, Object instanceValue )
	{
		switch ( eDataType.getClassifierID( ) )
		{
			case DataPackage.DATA :
				return convertDataToString( eDataType, instanceValue );
			default :
				throw new IllegalArgumentException( "The datatype '" + eDataType.getName( ) + "' is not a valid classifier" ); 
		}
	}
	/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	public Action createAction( )
	{
		ActionImpl action = new ActionImpl( );
		return action;
	}
	/**