Create translation from existing publication broken

[ryanfb]

Only on dev: https://sosol.airbrake.io/projects/20922/groups/1646400618549190995/notices/1646400615411431374

NoMethodError: undefined method `content' for nil:NilClass
app/models/hgv_trans_identifier.rb:102 in stub_text_structure
app/models/hgv_trans_identifier.rb:57 in new_from_template
app/controllers/identifiers_controller.rb:30 in create

[ryanfb]

Potentially a bug with reprints/associations, happened with a publication that had DDB identifier: papyri.info/ddbdp/bgu;15;2472
If I create a publication from that identifier, I get the message: This text is reprinted in papyri.info/ddbdp/bgu;1;239v, which is not associated with this publication (possibly a bug).
So the is_reprinted? filter in HGVTransIdentifier#related_text results in no related text being found.

[ryanfb]

Should probably just move HGVTransIdentifier#related_text to the Publication model, and only show the "create translation" link/button if it's not nil.