Fix exception when finding relationship to home person

Proposed bug fix to catch the reported exception by testing for None.
However, it's not a guaranteed fix because no data was provided to
test the bug.

Question remains what is the family tree that leads to that situation?
Is it a valid case? Should it be handled in a certain way that isn't
being done now? If it isn't valid, is it being captured by check and
repair database?

Fixes #13495

gramps/plugins/quickview/all_relations.py

@@ -380,7 +380,7 @@ def print_details_path(
                     for val in fam[1:]:
                         # TODO for Arabic, should the next comma be translated?
                         famstr += ", " + str(val + 1)
-                else:
+                elif fam is not None:
                     famstr = str(fam + 1)
                 sdoc.paragraph(_FMT_DET2 % (" ", par_str, birth_str, famstr))
                 counter = ""