Don't return Body for HEAD requests

handler.go

@@ -245,7 +245,12 @@ func (handler *Handler) headFile(w http.ResponseWriter, r *http.Request) {
 	id := r.URL.Query().Get(":id")
 	info, err := handler.dataStore.GetInfo(id)
 	if err != nil {
-		handler.sendError(w, err)
+		status := http.StatusInternalServerError
+		if os.IsNotExist(err) {
+			status = http.StatusNotFound
+		}
+		w.Header().Set("Content-Length", "0")
+		w.WriteHeader(status)
 		return
 	}