cmd/syncthing: Only delay next scan (via REST) if the scan succeeds

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3927

cmd/syncthing/gui.go

@@ -1140,18 +1140,17 @@ func (s *apiService) postDBScan(w http.ResponseWriter, r *http.Request) {
 	qs := r.URL.Query()
 	folder := qs.Get("folder")
 	if folder != "" {
-		nextStr := qs.Get("next")
-		next, err := strconv.Atoi(nextStr)
-		if err == nil {
-			s.model.DelayScan(folder, time.Duration(next)*time.Second)
-		}
-
 		subs := qs["sub"]
-		err = s.model.ScanFolderSubdirs(folder, subs)
+		err := s.model.ScanFolderSubdirs(folder, subs)
 		if err != nil {
 			http.Error(w, err.Error(), 500)
 			return
 		}
+		nextStr := qs.Get("next")
+		next, err := strconv.Atoi(nextStr)
+		if err == nil {
+			s.model.DelayScan(folder, time.Duration(next)*time.Second)
+		}
 	} else {
 		errors := s.model.ScanFolders()
 		if len(errors) > 0 {