Always return invite errors

This ensures we see a 404 page when looking up an invalid invite URL,
even if the user is logged in.

Ref T690

invites.go

@@ -110,6 +110,11 @@ func handleCreateUserInvite(app *App, u *User, w http.ResponseWriter, r *http.Re
 func handleViewInvite(app *App, w http.ResponseWriter, r *http.Request) error {
 	inviteCode := mux.Vars(r)["code"]
 
+	i, err := app.db.GetUserInvite(inviteCode)
+	if err != nil {
+		return err
+	}
+
 	if u := getUserSession(app, r); u != nil {
 		// check if invite belongs to another user
 		// error can be ignored as not important in this case
@@ -130,11 +135,6 @@ func handleViewInvite(app *App, w http.ResponseWriter, r *http.Request) error {
 		return nil
 	}
 
-	i, err := app.db.GetUserInvite(inviteCode)
-	if err != nil {
-		return err
-	}
-
 	p := struct {
 		page.StaticPage
 		Error   string