Fix Overview for crash when only one parent in family

Author: prculley

Overview/Overview.gpr.py

@@ -27,7 +27,7 @@
          id="Person Overview",
          name=_("Person Overview"),
          description = _("Gramplet showing an overview of events for a person"),
-         version = '1.0.11',
+         version = '1.0.12',
          gramps_target_version="5.1",
          status = STABLE,
          fname="Overview.py",
@@ -41,7 +41,7 @@
          id="Family Overview",
          name=_("Family Overview"),
          description = _("Gramplet showing an overview of events for a family"),
-         version = '1.0.11',
+         version = '1.0.12',
          gramps_target_version="5.1",
          status = STABLE,
          fname="Overview.py",

Overview/Overview.py

@@ -183,9 +183,12 @@ def display_person(self, active_handle):
             family = self.dbstate.db.get_family_from_handle(family_handle)
             father_handle = family.get_father_handle()
             mother_handle = family.get_mother_handle()
+            spouse = None
             if father_handle == active_handle:
-                spouse = self.dbstate.db.get_person_from_handle(mother_handle)
-            else:
+                if mother_handle:
+                    spouse = self.dbstate.db.get_person_from_handle(
+                        mother_handle)
+            elif father_handle:
                 spouse = self.dbstate.db.get_person_from_handle(father_handle)
             for event_ref in family.get_event_ref_list():
                 self.add_event_ref(event_ref, spouse)