Merge pull request #2900 from tchak/fix-cart-selection-param

Fix old carto exception when no selection is passed

app/controllers/users/carte_controller.rb

@@ -32,7 +32,7 @@ class Users::CarteController < UsersController
     @dossier = current_user_dossier
     @data = {}
 
-    geo_json = JSON.parse(params.required(:selection))
+    geo_json = JSON.parse(params.fetch(:selection, '[]'))
 
     if geo_json.first == ["error", "TooManyPolygons"]
       @error = true