Fix setting HTTP headers after write (#21833)

The headers can't be modified after it was send to the client.

routers/web/feed/profile.go

@@ -5,7 +5,6 @@
 package feed
 
 import (
-	"net/http"
 	"time"
 
 	activities_model "code.gitea.io/gitea/models/activities"
@@ -59,7 +58,6 @@ func showUserFeed(ctx *context.Context, formatType string) {
 
 // writeFeed write a feeds.Feed as atom or rss to ctx.Resp
 func writeFeed(ctx *context.Context, feed *feeds.Feed, formatType string) {
-	ctx.Resp.WriteHeader(http.StatusOK)
 	if formatType == "atom" {
 		ctx.Resp.Header().Set("Content-Type", "application/atom+xml;charset=utf-8")
 		if err := feed.WriteAtom(ctx.Resp); err != nil {

routers/web/web.go

@@ -604,7 +604,10 @@ func RegisterRoutes(m *web.Route) {
 
 	m.Group("", func() {
 		m.Get("/favicon.ico", func(ctx *context.Context) {
-			ctx.ServeFile(path.Join(setting.StaticRootPath, "public/img/favicon.png"))
+			ctx.SetServeHeaders(&context.ServeHeaderOptions{
+				Filename: "favicon.png",
+			})
+			http.ServeFile(ctx.Resp, ctx.Req, path.Join(setting.StaticRootPath, "public/img/favicon.png"))
 		})
 		m.Group("/{username}", func() {
 			m.Get(".png", func(ctx *context.Context) { ctx.Error(http.StatusNotFound) })