Diff breaks if csv deleted from base and head

[kdumontnu]

Description

Deleting a .csv file from both the base and head branch in a compare will result in a 500 error.

https://try.gitea.io/kdumontnu/test/compare/main...delete-csv

Gitea Version

d9c6cb7

Can you reproduce the bug on the Gitea demo site?

Yes

Log Gist

No response

Screenshots

No response

Git Version

No response

Operating System

No response

How are you running Gitea?

Seen on 1.17 initially. Reproduced on try.gitea.

Database

None

[lunny]

2023/02/17 02:58:03 ...s/context/context.go:231:HTML() [E] [63eeed3b-8] Render failed: template: repo/diff/csv_diff:3:15: executing "repo/diff/csv_diff" at <call .root.CreateCsvDiff .file .blobBase .blobHead>: error calling call: runtime error: invalid memory address or nil pointer dereference

[wxiaoguang]

Some contexts of this problem (just FYI):

• Issue PR Error 500 on CreateCsvDiff when trying to merge some branches: invalid memory address #19530
• PR Handle the error of a missing blob object fix #19530 #19552
• PR Fix CSV diff for added/deleted files #21189

[wxiaoguang]

OK, I fully understand the problem now. If a CSV file is deleted from both branch, then baseReader and headReader can both be nil.