message: Let prepareBuilder return undefined
diff: @@ -57,9 +57,9 @@ import {
  MsgUpdateAdminEncodeObject,
  } from "./encodeobjects";
  -function prepareBuilder(builder: string | undefined): string {
  - if (builder === undefined) {
  - return ""; // normalization needed by backend
  +function prepareBuilder(builder: string | undefined): string | undefined {
  + if (!builder) {
  + return undefined;
  } else {
  if (!isValidBuilder(builder)) throw new Error("The builder (Docker Hub image with tag) is not valid");
  return builder;
  