win32 - fix client size update when window is opened with extended client area (#13865)

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -1348,7 +1348,7 @@ namespace Avalonia.Win32
             else
                 SetFullScreen(newProperties.IsFullScreen);
 
-            if (!_isFullScreenActive)
+            if (!_isFullScreenActive && ((oldProperties.Decorations != newProperties.Decorations) || forceChanges))
             {
                 var style = GetStyle();