Prevent null pointer exception.
Update UGH to results of change goobi/goobi-ugh#13
Solve an open TODO
Remove unnecessary exception wrapping
Do not create typeless DocStruct
Do not try to add a metadatum if there is no docStruct
Merge pull request #284 from henning-gerhardt/issue_275

Fixes #275: Missing not null check in MetadatenImagesHelper.createPagination()
Merge pull request #285 from matthias-ronge/issue_283

Merge: Export copy rule and flat documents (#283)