   #
   patch "/flags/:name/boolean" do
     enabled = Utils.parse_bool(conn.params["enabled"])
-    flag_name = String.to_atom(name)
+    flag_name = String.to_existing_atom(name)
 
     if enabled do
       FunWithFlags.enable(flag_name)

  # to add a new group to a flag
  #
  post "/flags/:name/groups" do
    flag_name = String.to_atom(name)
    group_name = Utils.sanitize(conn.params["group_name"])

    case Utils.validate(group_name) do

  #
  delete "/flags/:name" do
    name
    |> String.to_existing_atom()
    |> FunWithFlags.clear()

    redirect_to conn, "/flags"
