Empty CASTEP band structures
The search finds several CASTEP calculations with an electronic band structure. It seems, however, that most (if not all) of the section_k_bands are empty. One example can be found here: https://nomad-lab.eu/prod/rae/beta/gui/entry/id/EMtbEy_XQ9aPZjJYRMJtDA/1HSP0tidKfWRUl0Xi76kkxYqyIgr/archive/section_run/section_single_configuration_calculation:1/section_k_band
If band structures are not present, then the parser should not open this section. If a band structure can be parsed, then the section should be populated with all the necessary metainfo (segments, energies, k-points).