Panic when clicking on a tag in a mirror

[gaydin]

• Gitea version (or commit ref): d293a2b (docker latest)
• Git version: 2.15.2
• Operating system: debian
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL): https://try.gitea.io/prompanic/prometheus/src/tag/v2.4.1
  • No
  • Not relevant
• Log gist: https://gist.github.com/gaydin/ebac500c7e5ee8078a7195adc40334d2

Description

gitea panic on click tag in mirror repository.
Example: https://try.gitea.io/prompanic/prometheus/src/tag/v2.4.1