[SAVer] Harmonize output on SAVer's Unknown answer.

No "empty parenthesis" anymore.

src/verification.ml

@@ -75,9 +75,15 @@ let answer_saver limit config env config_prover dataset_csv task =
     | Some filename -> filename
   in
   let answer = SAVer.call limit config env config_prover ~dataset task in
-  let prover_answer = answer.prover_answer in
-  let additional_info = Fmt.str "(%d/%d)" answer.nb_proved answer.nb_total in
-  (prover_answer, Some additional_info)
+  match answer.prover_answer with
+  | Call_provers.Unknown "" ->
+    let additional_info = Fmt.str "%d/%d" answer.nb_proved answer.nb_total in
+    (Call_provers.Unknown additional_info, None)
+  | Call_provers.Unknown _ ->
+    assert false (* By construction of SAVer's Unknown answer. *)
+  | prover_answer ->
+    let additional_info = Fmt.str "(%d/%d)" answer.nb_proved answer.nb_total in
+    (prover_answer, Some additional_info)
 
 let answer_generic limit config prover config_prover driver task =
   let task_prepared = Driver.prepare_task driver task in

tests/simple_ovo.t

@@ -39,4 +39,4 @@ Test verify
   > EOF
   [caisar] Goal G: Valid (2/2)
   [caisar] Goal H: Invalid (1/2)
-  [caisar] Goal I: Unknown () (0/2)
+  [caisar] Goal I: Unknown (0/2)