make more robust

core/models/caves.py

@@ -318,9 +318,12 @@ class Entrance(TroggleModel):
         except:
             stations = SurvexStation.objects.filter(name = station)
             print(f" # MULTIPLE stations found with same name '{station}' in Entrance {self}:")
+            if len(stations) > 1:
                 for s in stations:
                     print(f" # {s.id=} - {s.name}  {s.latlong()}") # .id is Django internal field, not one of ours
                 return stations[0]
+            else:
+                return None
 
     def exact_location(self):
         return self.single(self.exact_station)