wxiaoguang c5901b622d Avoid unnecessary 500 panic when a commit doesn't exist (#28719)
In #26851, it assumed that `Commit` always exists when
`PageIsDiff==true`.

But for a 404 page, the `Commit` doesn't exist, so the following code
would cause panic because nil value can't be passed as string parameter
to `IsMultilineCommitMessage(string)` (or the StringUtils.Cut in later
PRs)
2024-01-07 18:20:22 +08:00
..