Merge pull request #6266 from AvaloniaUI/fixes/osx-resizing-again

OSX: Fix showing window with no specified size.
# Conflicts:
#	native/Avalonia.Native/src/OSX/window.mm

native/Avalonia.Native/src/OSX/window.mm

@@ -52,6 +52,7 @@ public:
         [Window setBackingType:NSBackingStoreBuffered];
         
         [Window setOpaque:false];
+        [Window setContentView: StandardContainer];
     }
     
     virtual HRESULT ObtainNSWindowHandle(void** ret) override
@@ -124,7 +125,7 @@ public:
             SetPosition(lastPositionSet);
             UpdateStyle();
             
-            [Window setContentView: StandardContainer];
+            [Window setTitle:_lastTitle];
             
             if(ShouldTakeFocusOnShow() && activate)
             {