empty "Files and Indexes" section for summary records

[tiborsimko]

Current behaviour

On QA, for data summary records that do not have any files directly attached, but that only point to various daugther dataset records, we currently display empty "Files and Indexes" section to the users.

Example: https://opendata-qa.cern.ch/record/160000

Expected behaviour

No section "Files and Indexes" should be displayed if there are no files attached to a record.

Note

Stems from cernopendata/data-curation#259 (comment)