TypeError: Cannot read properties of undefined (reading 'replace')

The application is encountering the following error during execution:

```
[chat/completions] Error: {
message: "Cannot read properties of undefined (reading 'replace')",
stack: "TypeError: Cannot read properties of undefined (reading 'replace')\n" +
' at repairMarkdownFootnotes (D:\\deepresearch\\node-DeepResearch\\src\\utils\\text-tools.ts:43:8)\n' +
' at buildMdFromAnswer (D:\\deepresearch\\node-DeepResearch\\src\\utils\\text-tools.ts:8:10)\n' +
' at getResponse (D:\\deepresearch\\node-DeepResearch\\src\\agent.ts:963:38)\n' +
' at processTicksAndRejections (node:internal/process/task_queues:105:5)\n' +
' at async D:\\deepresearch\\node-DeepResearch\\src\\app.ts:551:9',
type: 'TypeError'
requestId: '1744119704425'
}
```