[gnome-sudoku/arnaudb/wip/gtk4: 13/27] Adapt size_allocate() method.

[Arnaud B. <arnaudb src gnome org>]

commit a0fab5cd57307f7e2ae1d3bb68d5906e2440f568
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Sun Apr 12 15:50:07 2020 +0200

    Adapt size_allocate() method.

 src/gnome-sudoku.vala | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)
---
diff --git a/src/gnome-sudoku.vala b/src/gnome-sudoku.vala
index d820d23..cf54b39 100644
--- a/src/gnome-sudoku.vala
+++ b/src/gnome-sudoku.vala
@@ -152,7 +152,7 @@ public class Sudoku : Gtk.Application
         var builder = new Builder.from_resource ("/org/gnome/Sudoku/ui/gnome-sudoku.ui");
 
         window = (ApplicationWindow) builder.get_object ("sudoku_app");
-        window.size_allocate.connect (size_allocate_cb);
+        window.size_allocate.connect (on_size_allocate);
         window.map.connect (init_state_watcher);
         window.set_default_size (settings.get_int ("window-width"), settings.get_int ("window-height"));
         if (settings.get_boolean ("window-is-maximized"))
@@ -231,11 +231,17 @@ public class Sudoku : Gtk.Application
         base.shutdown ();
     }
 
-    private void size_allocate_cb (Allocation allocation)
+    private void on_size_allocate (int width, int height, int baseline)
     {
         if (window_is_maximized || window_is_fullscreen || window_is_tiled)
             return;
-        window.get_size (out window_width, out window_height);
+        int? _window_width = null;
+        int? _window_height = null;
+        window.get_size (out _window_width, out _window_height);
+        if (_window_width == null || _window_height == null)
+            return;
+        window_width = (!) _window_width;
+        window_height = (!) _window_height;
     }
 
     private inline void init_state_watcher ()