NoCommitterAccount: user does not exist

[Pofilo]

• Gitea version (or commit ref): 1.3.3
• Git version: 2.7.4
• Operating system: Ubuntu 16.04.4 LTS
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No (no access to logs)
  • Not relevant
• Log gist:

Description

I'm running my own instance of Gitea and I have some mirrors (linked to github mostly).
I have a lot of logs like this one which are errors:

[...ea/models/gpg_key.go:385 ParseCommitWithSignature()] [E] NoCommitterAccount: user does not exist [uid: 0, name: noreply@github.com, keyid: 0]

I don't know if this is relevant to the screenshot, plus I don't find any dock explaining what it means.

Does someone know what it means ? I have so many logs due to this thing I don't understand.

Screenshots

[lafriks]

Yes this is not real error and should be lowered to information level in log