Missing workflow returns 500 from workflow type endpoint

### What happened?

The workflow type endpoint dereferences a missing DAO result. An authenticated request for a workflow ID that does not exist returns 500 instead of 404.

Before: missing workflow returns 500

After: missing workflow returns 404

### How to reproduce?

1. Start the local development stack.
2. Sign in as a regular or admin user.
3. Send `GET /api/workflow/type/2147483647`.

The local response was 500:

```text
{"code":500,"message":"There was an error processing your request."}
```

### Version/Branch

1.3.0-incubating-SNAPSHOT (main)

### Commit Hash (Optional)

7d57cd6ef1

### Relevant log output

The request reaches `workflowDao.fetchOneByWid`, receives null, and then calls `workflow.getIsPublic`.

Start the local development stack, authenticate, and reproduce GET /api/workflow/type/2147483647. Trace the endpoint through workflowDao.fetchOneByWid and verify the missing workflow case; done means the same request returns HTTP 404 rather than 500 for both regular and admin users.

Written by the indexing model from the issue text.