Always set PullRequestWorkInProgressPrefixes in PrepareViewPullInfo (#18713) (#18737)

Backport #18713

Move setting PullRequestWorkInProgressPrefixes to the start of PrepareViewPullInfo.

Fix #18706

Signed-off-by: Andrew Thornton <art27@cantab.net>

routers/web/repo/pull.go

@@ -392,6 +392,8 @@ func PrepareMergedViewPullInfo(ctx *context.Context, issue *models.Issue) *git.C
 
 // PrepareViewPullInfo show meta information for a pull request preview page
 func PrepareViewPullInfo(ctx *context.Context, issue *models.Issue) *git.CompareInfo {
+	ctx.Data["PullRequestWorkInProgressPrefixes"] = setting.Repository.PullRequest.WorkInProgressPrefixes
+
 	repo := ctx.Repo.Repository
 	pull := issue.PullRequest
 
@@ -575,8 +577,6 @@ func PrepareViewPullInfo(ctx *context.Context, issue *models.Issue) *git.Compare
 		ctx.Data["IsNothingToCompare"] = true
 	}
 
-	ctx.Data["PullRequestWorkInProgressPrefixes"] = setting.Repository.PullRequest.WorkInProgressPrefixes
-
 	if pull.IsWorkInProgress() {
 		ctx.Data["IsPullWorkInProgress"] = true
 		ctx.Data["WorkInProgressPrefix"] = pull.GetWorkInProgressPrefix()