SysML: Avoid NPE when exporting logical architecture only

When exporting a logical architecture without the data dictory that is referenced by it, below NPE is thrown. The expected behavior is that the SysML exporter complains that the datatype is not know.

java.lang.NullPointerException at org.fortiss.af3.sysml.utils.DataDictionaryUMLPackageFactory.setMemberType(DataDictionaryUMLPackageFactory.java:133) at org.fortiss.af3.sysml.AF3SysMLToEMFMapping.addAnnotation(AF3SysMLToEMFMapping.java:300) at org.fortiss.af3.sysml.AF3SysMLToEMFMapping.addAnnotationsComponents(AF3SysMLToEMFMapping.java:237) at org.fortiss.af3.sysml.AF3SysMLToEMFMapping.myCreateLogicalMaps(AF3SysMLToEMFMapping.java:210) at org.fortiss.af3.sysml.AF3SysMLToEMFMapping.myCreateLogicalMaps(AF3SysMLToEMFMapping.java:206) at org.fortiss.af3.sysml.AF3SysMLToEMFMapping.myCreateLogicalMaps(AF3SysMLToEMFMapping.java:206) at org.fortiss.af3.sysml.AF3SysMLToEMFMapping.myCreateLogicalMaps(AF3SysMLToEMFMapping.java:206) at org.fortiss.af3.sysml.AF3SysMLToEMFMapping.(AF3SysMLToEMFMapping.java:166) at org.fortiss.af3.sysml.AF3SysMLExtractor.(AF3SysMLExtractor.java:179) at org.fortiss.af3.sysml.ui.SysMLExportAction.run(SysMLExportAction.java:83) at org.eclipse.jface.action.Action.runWithEvent(Action.java:474)