500 error when browsing a repo where the only commits are tags.

[sollie]

• Gitea version (or commit ref): 1.1.0
• Git version: Not relevant
• Operating system: Ubuntu 16.04
• 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/sollie/test
  • No
  • Not relevant
• Log gist:

Description

Create new repo, push tag. Browsing repo produces a 500 error.
Pushing to master fixes it.

Relevant log entry:
2017/05/11 12:33:01 [...ules/context/repo.go:308 func1()] [E] GetBranches: exit status 1