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/DataPackage.java
* Returns the meta object for the containment reference list '{@link org.eclipse.birt.chart.model.data.SeriesDefinition#getSeriesDefinitions <em>Series Definitions</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for the containment reference list '<em>Series Definitions</em>'.
	 * @see org.eclipse.birt.chart.model.data.SeriesDefinition#getSeriesDefinitions()
	 * @see #getSeriesDefinition()
	 * @generated
	 */
	EReference getSeriesDefinition_SeriesDefinitions( );
	/**
	 * Returns the meta object for the containment reference '{@link org.eclipse.birt.chart.model.data.SeriesDefinition#getFormatSpecifier <em>Format Specifier</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for the containment reference '<em>Format Specifier</em>'.
	 * @see org.eclipse.birt.chart.model.data.SeriesDefinition#getFormatSpecifier()
	 * @see #getSeriesDefinition()
	 * @generated
	 */
	EReference getSeriesDefinition_FormatSpecifier( );
	/**
	 * Returns the meta object for the containment reference list '{@link org.eclipse.birt.chart.model.data.SeriesDefinition#getSeries <em>Series</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for the containment reference list '<em>Series</em>'.
	 * @see org.eclipse.birt.chart.model.data.SeriesDefinition#getSeries()
	 * @see #getSeriesDefinition()
	 * @generated
	 */
	EReference getSeriesDefinition_Series( );
	/**
	 * Returns the meta object for the containment reference '{@link org.eclipse.birt.chart.model.data.SeriesDefinition#getGrouping <em>Grouping</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for the containment reference '<em>Grouping</em>'.