allow using SetFont(wxNullFont) to reset the font as per documented behaviour (#3238)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@54664 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/window.cpp

@@ -871,7 +871,11 @@ bool wxWindowMSW::SetFont(const wxFont& font)
     HWND hWnd = GetHwnd();
     if ( hWnd != 0 )
     {
-        WXHANDLE hFont = m_font.GetResourceHandle();
+        // note the use of GetFont() instead of m_font: our own font could have
+        // just been reset and in this case we need to change the font used by
+        // the native window to the default for this class, i.e. exactly what
+        // GetFont() returns
+        WXHANDLE hFont = GetFont().GetResourceHandle();
 
         wxASSERT_MSG( hFont, wxT("should have valid font") );