fix: ui render with empty artifact

[tczhao]

Fixes #14226

Tested, UI displays fine in both scenario and is able to display artifact correctly

workflow with empty artifact

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: input-artifact-s3-
spec:
  entrypoint: input-artifact-s3-example
  templates:
  - name: input-artifact-s3-example
    inputs:
      parameters:
        - name: path
          value: ""
      artifacts:
      - name: my-art
        path: /my-artifact
        s3:
          key: "{{inputs.parameters.path}}"
        optional: true
    container:
      image: debian:latest
      command: [sh, -c]
      args: ["echo hello world"]

workflow with actual artifact
https://github.com/argoproj/argo-workflows/blob/14121-actor-label-email-fix/examples/artifact-passing.yaml

Motivation

Modifications

Verification

Documentation