[GITEA] Handle non-existant commit in Archive request

- When a user requests a archive of a non-existant commit
`git.ErrNotExist` is returned, but was not gracefully handled resulting
in a 500 error.
- Doesn't exist in v1.22 due to it being refactored away in
cbf923e87b
- Adds integration test.

routers/web/repo/repo.go

@@ -421,7 +421,7 @@ func Download(ctx *context.Context) {
 	if err != nil {
 		if errors.Is(err, archiver_service.ErrUnknownArchiveFormat{}) {
 			ctx.Error(http.StatusBadRequest, err.Error())
-		} else if errors.Is(err, archiver_service.RepoRefNotFoundError{}) {
+		} else if errors.Is(err, archiver_service.RepoRefNotFoundError{}) || git.IsErrNotExist(err) {
 			ctx.Error(http.StatusNotFound, err.Error())
 		} else {
 			ctx.ServerError("archiver_service.NewRequest", err)

tests/integration/repo_test.go

@@ -720,3 +720,12 @@ func TestRenamedFileHistory(t *testing.T) {
 		htmlDoc.AssertElement(t, ".ui.bottom.attached.header", false)
 	})
 }
+
+func TestArchiveRequest(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	session := loginUser(t, "user2")
+
+	req := NewRequest(t, "GET", "/user2/repo1/archive/a480fe666d6f550787b6cc85047b966d1f8d6bbf.zip")
+	session.MakeRequest(t, req, http.StatusNotFound)
+}