1.16.0: Workflow editor crashes with HTTP Request / Iteration nodes - "Cannot read properties of undefined (reading 'map')"

## Self Checks

- [x] I have searched for existing issues: https://github.com/langgenius/dify/issues?q=is%3Aissue+%22reading+%27map%27%22+workflow
- [x] This is a bug report, not a feature request or question

## Dify version

1.16.0 (upgraded from 1.14.2)

## Cloud or Self Hosted

Self Hosted (Docker)

## Steps to reproduce

1. Create a new Chatflow / Advanced Chat app
2. Add an **HTTP Request** node or **Iteration** node to the workflow
3. Save and try to open the workflow editor
4. The page crashes with "Application error: a client-side exception" and a "重試" (Retry) button

## Console Error

```
TypeError: Cannot read properties of undefined (reading 'map')
at 0re5ausc4xup1.js:1:92282

AbortError: signal is aborted without reason
at 0re5ausc4xup1.js:1:123703
```

## Expected Behavior

Workflow editor should render normally with HTTP Request and Iteration nodes.

## Actual Behavior

The workflow editor crashes completely. The error occurs even with freshly created (empty) workflows that contain these node types. Workflows without these nodes (Start, Code, IF, Answer, Variable Assigner) work fine.

## Additional Context

- Upgraded from 1.14.2 to 1.16.0, issue exists on both versions
- Also tried deleting and recreating the affected workflows via API - same result
- Backend API returns valid workflow data (confirmed via curl)
- The bug is a React frontend crash, not a backend issue
- Same JS chunk `0re5ausc4xup1.js` crashes consistently

## Impact

Cannot edit or view any workflow containing HTTP Request or Iteration nodes, making these node types unusable in Dify 1.16.0.

Start in the workflow editor entry point and reproduce the crash with a fresh workflow containing an HTTP Request or Iteration node; use the browser console to confirm the Cannot read properties of undefined (reading 'map') error in chunk 0re5ausc4xup1.js. Compare the rendered node data with a workflow containing only Start, Code, IF, Answer, or Variable Assigner nodes, and verify that both affected node types open without a client-side exception.

Written by the indexing model from the issue text.