Associate the window with the sizer in wxSizer::Replace()

If wxSizerItem passed to Replace() contains a window, the window must be
associated with the sizer to ensure that it is uncoupled from it when it
is destroyed.

Add a simple test which resulted in a use-after-free before but passes
now.

src/common/sizer.cpp

@@ -883,6 +883,9 @@ bool wxSizer::Replace( size_t old, wxSizerItem *newitem )
 
     delete item;
 
+    if (wxWindow* const w = newitem->GetWindow())
+        w->SetContainingSizer(this);
+
     return true;
 }