[gnome-tetravex] More vala-ish code.

[Arnaud B. <arnaudb src gnome org>]

commit 5696db89e372f44b5ff28956fc7ee09a8bb438e5
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Tue Nov 5 22:11:00 2019 +0100

    More vala-ish code.

 src/gnome-tetravex.vala | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)
---
diff --git a/src/gnome-tetravex.vala b/src/gnome-tetravex.vala
index 4534f00..054a1b2 100644
--- a/src/gnome-tetravex.vala
+++ b/src/gnome-tetravex.vala
@@ -641,8 +641,7 @@ private class Tetravex : Gtk.Application
             dialog.add_buttons (_("_Keep Playing"),   ResponseType.REJECT,
 
         /* Translators: popup dialog possible answer (with a mnemonic that appears pressing Alt); appearing 
when user clicks "New Game" from the hamburger menu; other possible answer is "_Keep Playing" */
-                                _("_Start New Game"), ResponseType.ACCEPT,
-                                null);
+                                _("_Start New Game"), ResponseType.ACCEPT);
 
             int response = dialog.run ();
             dialog.destroy ();
@@ -713,8 +712,7 @@ private class Tetravex : Gtk.Application
             dialog.add_buttons (_("_Keep Playing"), ResponseType.REJECT,
 
             /* Translators: popup dialog possible answer (with a mnemonic that appears pressing Alt); 
appearing when user clicks the "Give up" button in the bottom bar; other possible answer is "_Keep Playing" */
-                                _("_Give Up"),      ResponseType.ACCEPT,
-                                null);
+                                _("_Give Up"),      ResponseType.ACCEPT);
 
             int response = dialog.run ();
             dialog.destroy ();
@@ -758,8 +756,7 @@ private class Tetravex : Gtk.Application
             dialog.add_buttons (_("_Keep Playing"),   ResponseType.REJECT,
 
         /* Translators: popup dialog possible answer (with a mnemonic that appears pressing Alt); appearing 
when user changes size from the hamburger menu submenu, while a game is started; other possible answer is 
"_Keep Playing" */
-                                _("_Start New Game"), ResponseType.ACCEPT,
-                                null);
+                                _("_Start New Game"), ResponseType.ACCEPT);
 
             int response = dialog.run ();
             dialog.destroy ();