Graph results in 500 error after upgrade

[hauke68]

• Gitea version (or commit ref): 1.14.1
• Git version: 2.1.4
• Operating system: Debian, gitea runs as downloaded binary, started by SysV
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL):
  • No
• Log gist: https://gist.github.com/hauke68/bab3c33fba4f81d5dff295357cdb0e28

Description

I upgraded gitea from 1.13.0 via 1.13.7 to 1.14.1 and after that, calling the graph results in a 500 error. See https://opengit.hauke-zuehl.de/hauke/Skripte/graph for an example.

Never had problems before.

Screenshots

[zeripath]

Already fixed and backported. See #15517 & #15530 should be v1.14.2