SSDM-3348: fixing dto inconsistencies: avoiding npe with null fetch options

...s/openbis/generic/asapi/v3/dto/attachment/Attachment.java

...thz/sis/openbis/generic/asapi/v3/dto/dataset/DataSet.java

.../sis/openbis/generic/asapi/v3/dto/dataset/LinkedData.java

...is/openbis/generic/asapi/v3/dto/dataset/PhysicalData.java

...z/sis/openbis/generic/asapi/v3/dto/deletion/Deletion.java

...s/openbis/generic/asapi/v3/dto/experiment/Experiment.java

...enbis/generic/asapi/v3/dto/global/GlobalSearchObject.java

...is/openbis/generic/asapi/v3/dto/history/HistoryEntry.java

...z/sis/openbis/generic/asapi/v3/dto/material/Material.java

.../ethz/sis/openbis/generic/asapi/v3/dto/person/Person.java

...thz/sis/openbis/generic/asapi/v3/dto/project/Project.java

.../ethz/sis/openbis/generic/asapi/v3/dto/sample/Sample.java

...ch/ethz/sis/openbis/generic/asapi/v3/dto/space/Space.java

...ava/ch/ethz/sis/openbis/generic/asapi/v3/dto/tag/Tag.java

...s/openbis/generic/asapi/v3/dto/vocabulary/Vocabulary.java

...enbis/generic/asapi/v3/dto/vocabulary/VocabularyTerm.java