[gnome-chess] Cancel move if promotion type selector is closed

[Sahil Sareen <ssareen src gnome org>]

commit ed9ffc4ba2147b252b22122ff6be35d5b894583b
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Sun Jan 11 11:35:07 2015 -0600

    Cancel move if promotion type selector is closed
    
    https://bugzilla.gnome.org/show_bug.cgi?id=742762

 src/chess-scene.vala |    6 ++++--
 src/gnome-chess.vala |    7 ++-----
 2 files changed, 6 insertions(+), 7 deletions(-)
---
diff --git a/src/chess-scene.vala b/src/chess-scene.vala
index 640c528..9d9ea5e 100644
--- a/src/chess-scene.vala
+++ b/src/chess-scene.vala
@@ -77,7 +77,7 @@ public class ChessScene : Object
     private double animation_time;
 
     public signal bool is_human (ChessPlayer player);
-    public signal PieceType choose_promotion_type ();
+    public signal PieceType? choose_promotion_type ();
     public signal void changed ();
 
     public int selected_rank = -1;
@@ -229,7 +229,9 @@ public class ChessScene : Object
                 (rank == 0 || rank == 7))
             {
                 /* Prompt user for selecting promotion type */
-                PieceType promotion_selection = choose_promotion_type ();
+                PieceType? promotion_selection = choose_promotion_type ();
+                if (promotion_selection == null)
+                    return;
                 game.current_player.move_with_coords (selected_rank,
                     selected_file, rank, file, true, promotion_selection);
                 selected_rank = selected_file = -1;
diff --git a/src/gnome-chess.vala b/src/gnome-chess.vala
index 65a3cd4..8887581 100644
--- a/src/gnome-chess.vala
+++ b/src/gnome-chess.vala
@@ -261,7 +261,7 @@ public class ChessApplication : Gtk.Application
         window.show ();
     }
 
-    public PieceType show_promotion_type_selector ()
+    public PieceType? show_promotion_type_selector ()
     {
         Gtk.Builder promotion_type_selector_builder;
 
@@ -298,7 +298,7 @@ public class ChessApplication : Gtk.Application
 
         promotion_type_selector_builder.connect_signals (this);
 
-        PieceType selection;
+        PieceType? selection = null;
         int choice = promotion_type_selector_dialog.run ();
         switch (choice)
         {
@@ -314,9 +314,6 @@ public class ChessApplication : Gtk.Application
             case PromotionTypeSelected.BISHOP:
                 selection = PieceType.BISHOP;
                 break;
-            default:
-                selection = PieceType.QUEEN;
-                break;
         }
         promotion_type_selector_dialog.destroy ();