Describe the bug

Generation of (smart) links to issues and PRs don't work in versions higher than 0.12.

Gogs version and commit

Tried with 0.12.3 (several instances, different servers) and 0.13.0-dev

It happens also in https://try.gogs.io (see attached screenshots)

Git version

$ git version
git version 2.30.1

Operating system

FreeBSD, Debian

Database

PostgreSQL 11, MySQL 5.5

To Reproduce
Steps to reproduce the behavior:

1. open an issue, in the description write the number of another issue, like Users sign in/out #2
2. click on preview, in the rendered preview, Users sign in/out #2 is a link to issue number 2
3. click save, in the rendered page with the new issue, Users sign in/out #2 is not a link to issue number 2

Can you reproduce the bug at https://try.gogs.io?

Yes

https://try.gogs.io/14mroot/testing-issue/issues/2

Expected behavior

Write #{issue} and a link to the issue to be rendered

Actual behavior

Wrote #{issue} and a link to the issue is not rendered

Screenshots

Attached are three screenshots with the described behaviour in try.gogs.io

Additional context