[SAVer] Option on dataset csv.

src/verification.ml

@@ -61,8 +61,8 @@ let answer_saver limit config task env prover dataset_csv =
   let handle_task_saver task env dataset_csv command =
     let dataset_filename =
       match dataset_csv with
-      | "" -> failwith "Error, no dataset provided for SAVer."
-      | s -> s
+      | None -> failwith "Error, no dataset provided for SAVer."
+      | Some s -> s
     in
     let goal = Task.task_goal_fmla task in
     let eps, svm_filename =
@@ -190,7 +190,6 @@ let verify ?(debug = false) format loadpath ?memlimit ?timeout prover
   let env, config = create_env loadpath in
   let steplimit = None in
   let steps = match steplimit with Some 0 -> None | _ -> steplimit in
-  let dataset_csv = Option.value dataset_csv ~default:"" in
   let limit =
     let memlimit =
       Option.value memlimit ~default:Whyconf.(memlimit (get_main config))