Fixed the case when stations is None

pyrmv/classes/Client.py

@@ -198,12 +198,14 @@ class Client():
         if isinstance(station_to, Stop):
             station_to = station_to.ext_id
 
-        new_stations = []
-        for stop in stations:
-            if isinstance(stop, Stop):
-                new_stations.append(stop.ext_id)
-            else:
-                new_stations.append(stop)
+        if stations != None:
+            new_stations = []
+            for stop in stations:
+                if isinstance(stop, Stop):
+                    new_stations.append(stop.ext_id)
+                else:
+                    new_stations.append(stop)
+            stations = new_stations
 
         if search_mode == None:
             search_mode = None
@@ -235,7 +237,7 @@ class Client():
             companies=companies,
             lines=lines,
             lineids=line_ids,
-            stations=new_stations,
+            stations=stations,
             fromstation=station_from,
             tostation=station_to,
             bothways=both_ways,