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 numberDataSet;
	}
	/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	public OrthogonalSampleData createOrthogonalSampleData( )
	{
		OrthogonalSampleDataImpl orthogonalSampleData = new OrthogonalSampleDataImpl( );
		return orthogonalSampleData;
	}
	/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	public Query createQuery( )
	{
		QueryImpl query = new QueryImpl( );
		return query;
	}
	/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	public Rule createRule( )
	{
		RuleImpl rule = new RuleImpl( );
		return rule;
	}
	/**