Fix the Unsellable judgment error introduced by fc1219

[DeathFishAtEase]

Fix the bug introduced by commit fc12197 where the Unsellable value incorrectly corresponded to whether it could be sold.

[phoboscn-bot]

To Chinese users:
This pull request has been mentioned on Phobos CN. There might be relevant details there:

致中文用户：
此拉取请求已在 Phobos CN 上被提及。那里可能有相关详细信息：

https://www.phoboscn.top/t/topic/376/3

[github-actions]

Nightly build for this pull request:

• compiled-dll-8c74ada201961c8623c0f22b98658838b7ce1288.zip
  These artifacts will expire in 90 days and will not be available for download after that time.

This comment is automatic and is meant to allow guests to get latest nightly builds for this pull request without registering. It is updated on every successful build.

[DeathFishAtEase]

Tested by https://www.phoboscn.top/t/topic/376/6