bug(scan): http_crawl fails with TypeError('can only join an iterable')

[psyray]

Current Behavior

According to the latest modifications, under certain circumstance, there is a problem with the save_subdomain_metadata method

The HTTPx response does not contains any iterable data because of the error.

{
  "timestamp": "2024-06-19T13:25:14.213159887Z",
  "url": "",
  "input": "",
  "error": "context deadline exceeded (Client.Timeout exceeded while awaiting headers)",
  "words": 0,
  "lines": 0,
  "content_length": 0,
  "failed": true
}

A check need to be added to prevent this error

Expected Behavior

Http_crawl should run fine

Steps To Reproduce

Do a scan and maybe you could have the erreor if a request fails

Environment

- reNgine: 2.0.6
- OS: Debian
- Python: 3.10

Anything else?

No response

Acknowledgements

• This issue is not a duplicate of an existing bug report.
• I have chosen an appropriate title.
• All requested information has been provided properly.