1.27.5 - Cant convert nodes to subgraph

### Prerequisites

- [x] I am running the latest version of ComfyUI

Errors in console

```
Uncaught TypeError: Cannot read properties of null (reading 'links')
at setgetnodes.js:452:32
at Array.filter ()
at GetNode.validateLinks (setgetnodes.js:451:29)
at GetNode.onConnectionsChange (setgetnodes.js:417:11)
at GetNode.configure (LGraphNode.ts:816:14)
at multiClone (subgraphUtils.ts:228:13)
at LGraph.convertToSubgraph (LGraph.ts:1509:25)
at app.graph.convertToSubgraph (use_everywhere.js:371:45)
at HTMLDivElement.callback (LGraphCanvas.ts:8060:29)
at HTMLDivElement.n (extensions-DFtJQYTL.js:1:144819)
```

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-5630-1-27-5-Cant-convert-nodes-to-subgraph-2726d73d36508174bcb3fa3c06036813) by [Unito](https://www.unito.io)