Can't search repository by topic name

[appleboy]

• Gitea version (or commit ref): ae9dd23
• Git version: 2.17.1
• Operating system:
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No
  • Not relevant
• Log gist:

Description

According to #3711 (comment) comments. User can't search repository by topic name.