Update a Tankoubon API endpoint does not delete the summary and tags values

[junpet]

LRR Version and OS
LANraragi 0.9.3 - Law (Earthlings on Fire)
Debian GNU/Linux bookworm 12.8 x86_64
Docker version 27.4.1, build b9d17ea

Bug Details
Update a Tankoubon API endpoint (PUT http://lrr.tvc-16.science/api/tankoubons/:id) does not delete the summary and tags values. I tried with empty string

{
  "metadata": {
    "summary": "",
    "tags": ""
  }
}

and null

{
  "metadata": {
    "summary": null,
    "tags": null
  }
}

but it does not delete the previous values. I tried updating only one of the metadata, but the result is the same.

[EfronC]

Yes, the issue is that I didn't expect to erase the summary and tags, so the check I use to verify that the field is defined also skips it if is "". Will fix it.