Correct returns when no path could be found

Methods that return an array when a path is found now return [] instead of None if no path can be found

geotrek/core/path_router.py

@@ -150,7 +150,7 @@ def get_edge_weight(self, edge_id):
     def get_route(self, steps):
         self.steps = steps
         line_strings = self.compute_list_of_paths()
-        if line_strings is None:
+        if line_strings == []:
             return None
 
         multi_line_string = GeometryCollection(line_strings, srid=settings.SRID)
@@ -166,8 +166,8 @@ def compute_list_of_paths(self):
             from_step = self.steps[i]
             to_step = self.steps[i + 1]
             line_strings = self.compute_two_steps_line_strings(from_step, to_step)
-            if line_strings is None:
-                return None
+            if line_strings == []:
+                return []
             merged_line_string = self.merge_line_strings(line_strings)
             all_line_strings.append(merged_line_string)
         return all_line_strings
@@ -178,8 +178,8 @@ def compute_two_steps_line_strings(self, from_step, to_step):
 
         shortest_path = self.get_shortest_path(from_node_info['node_id'],
                                                to_node_info['node_id'])
-        if shortest_path is None:
-            return None
+        if shortest_path == []:
+            return []
         line_strings = self.node_list_to_line_strings(shortest_path,
                                                       from_node_info, to_node_info)
 
@@ -417,7 +417,7 @@ def get_node_id_per_idx(node_idx):
         while current_node_id != from_node_id:
             if current_node_idx < 0:
                 # The path ends here but this node is not the destination
-                return None
+                return []
             current_node_idx = predecessors[current_node_idx]
             current_node_id = get_node_id_per_idx(current_node_idx)
             path.append(current_node_id)