Making pattern matching exaustive

pfx/basic/eval.ml

@@ -12,7 +12,7 @@ let string_of_state (cmds,stack) =
 (* Question 4.2 *)
 let step state =
   match state with
-  (* | [], _ -> Error("Nothing to step",state) *)
+  | [], _ -> Error("Nothing to step",state)
   (* Exception configurations *)
   | Pop::_, [] -> Error("Nothing to pop",state)
   | Swap::_, _::[] -> Error("Nothing to swap",state)