RDF export error: rdf.common.references()

[jessesnyder]

Exception thrown while running weekly RDF export:

2022-03-24 13:03:27 ERROR pleiades.rdf Failed to add object graph of <Place at /plone/places/50124> to dump batch: cannot concate
nate 'str' and 'int' objects
Traceback (most recent call last):
  File "./dump-scripts/rdf.py", line 151, in <module>
    g += PlaceGrapher(site, app).place(obj, vocabs=False)
  File "/srv/python27-apps/pleiades4/src/pleiades.rdf/pleiades/rdf/common.py", line 561, in place
    g = self.references(obj, g, locn_subj)
  File "/srv/python27-apps/pleiades4/src/pleiades.rdf/pleiades/rdf/common.py", line 330, in references
    citation_detail)
TypeError: cannot concatenate 'str' and 'int' objects
2022-03-24 13:09:08 ERROR pleiades.rdf Exception caught computing grid extent for <Location at /plone/places/589659/batlas-location>