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/DataPackageImpl.java
createEAttribute( dataSetEClass, DATA_SET__VALUES );
		dateTimeDataElementEClass = createEClass( DATE_TIME_DATA_ELEMENT );
		createEAttribute( dateTimeDataElementEClass,
				DATE_TIME_DATA_ELEMENT__VALUE );
		dateTimeDataSetEClass = createEClass( DATE_TIME_DATA_SET );
		differenceDataSetEClass = createEClass( DIFFERENCE_DATA_SET );
		ganttDataSetEClass = createEClass( GANTT_DATA_SET );
		numberDataElementEClass = createEClass( NUMBER_DATA_ELEMENT );
		createEAttribute( numberDataElementEClass, NUMBER_DATA_ELEMENT__VALUE );
		numberDataSetEClass = createEClass( NUMBER_DATA_SET );
		orthogonalSampleDataEClass = createEClass( ORTHOGONAL_SAMPLE_DATA );
		createEAttribute( orthogonalSampleDataEClass,
				ORTHOGONAL_SAMPLE_DATA__DATA_SET_REPRESENTATION );
		createEAttribute( orthogonalSampleDataEClass,
				ORTHOGONAL_SAMPLE_DATA__SERIES_DEFINITION_INDEX );
		queryEClass = createEClass( QUERY );
		createEAttribute( queryEClass, QUERY__DEFINITION );
		createEReference( queryEClass, QUERY__RULES );
		ruleEClass = createEClass( RULE );
		createEAttribute( ruleEClass, RULE__TYPE );
		createEAttribute( ruleEClass, RULE__VALUE );
		sampleDataEClass = createEClass( SAMPLE_DATA );
		createEReference( sampleDataEClass, SAMPLE_DATA__BASE_SAMPLE_DATA );
		createEReference( sampleDataEClass, SAMPLE_DATA__ORTHOGONAL_SAMPLE_DATA );
		createEReference( sampleDataEClass, SAMPLE_DATA__ANCILLARY_SAMPLE_DATA );
		seriesDefinitionEClass = createEClass( SERIES_DEFINITION );
		createEReference( seriesDefinitionEClass, SERIES_DEFINITION__QUERY );
		createEReference( seriesDefinitionEClass,
				SERIES_DEFINITION__SERIES_PALETTE );
		createEReference( seriesDefinitionEClass,