Add @mbacarella's check for complete absence of grpc-status

lib/grpc-async/client.ml

@@ -67,7 +67,11 @@ let call ~service ~rpc ?(scheme = "https") ~handler ~do_request
      Ivar.fill handler_res_ivar handler_res;
      return ());
   let%bind out = Ivar.read out_ivar in
-  let%bind trailers_status = Ivar.read trailers_status_ivar in
+  let%bind trailers_status =
+    (* In case no grpc-status appears in headers or trailers. *)
+    if Ivar.is_full trailers_status_ivar then Ivar.read trailers_status_ivar
+    else return (Grpc.Status.v ~message:"Server did not return grpc-status" Grpc.Status.Unknown) 
+  in
   match out with
   | Error _ as e -> return e
   | Ok out -> return (Ok (out, trailers_status))

lib/grpc-lwt/client.ml

@@ -64,7 +64,12 @@ let call ~service ~rpc ?(scheme = "https") ~handler ~do_request
       let+ handler_res = handler write_body read_body in
       Lwt.wakeup_later handler_res_notify handler_res);
   let* out in
-  let+ status in
+  let+ status = 
+    match Lwt.state status with 
+    (* In case no grpc-status appears in headers or trailers. *)
+    | Sleep -> let+ status in status
+    | _ -> Lwt.return @@ Grpc.Status.v ~message:"Server did not return grpc-status" Grpc.Status.Unknown
+  in
   match out with Error _ as e -> e | Ok out -> Ok (out, status)
 
 module Rpc = struct