Workflow Loading and Closing Logic Issues

### Prerequisites

- [x] I am running the latest version of ComfyUI
- [x] I have searched existing issues to make sure this isn't a duplicate
- [x] I have tested with all custom nodes disabled ([see how](https://docs.comfy.org/troubleshooting/custom-node-issues#step-1%3A-test-with-all-custom-nodes-disabled))

### What happened?

Loading and closing certain workflows in ComfyUI will produce issues.

1. Loading an Image with certain non-Comfy metadata will recreate a basic Comfy workflow. However, the workflow will be created on top of whichever workflow tab is currently opened instead of creating a new tab, overwriting the existing workflow.

https://github.com/user-attachments/assets/050012ee-ccd7-494e-88d6-f77f640e0cf9

2. Closing a workflow with missing nodes does not close it properly. Instead, it will seemingly break the workflow closing and switching logic, no longer allowing users to return to other workflows. Refreshing the browser doesn't help - the only solution is to select and delete all nodes in the workflow with missing nodes before closing.

https://github.com/user-attachments/assets/cfe715d5-6fdb-4291-abad-bd6f0e51edb7

### Steps to Reproduce

Videos Provided.

### How is this affecting you?

Feature doesn't work as expected

### ComfyUI Frontend Version

1.34.9

### Browser

Edge

### Console Errors

```javascript

```

### Logs

```shell

```

### Additional Context

_No response_

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-7840-Workflow-Loading-and-Closing-Logic-Issues-2de6d73d36508189bdf8d7f94a5acfb6) by [Unito](https://www.unito.io)