fix error in last_locaion

app/models/user.py

@@ -58,7 +58,8 @@ class User(UserMixin, db.Model):
             return None
         if game is None:
             return self.locations[-1]
-        return self.locations_during_game(game)[-1]
+        locations_during_game = self.locations_during_game(game)
+        return locations_during_game[-1] if locations_during_game else None
 
     def role_in_game(self, game):
         '''Returns the role as Role enum of player in given game. Returns None if player does not participate in game'''