backport of r61148

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_9_0_BRANCH@61149 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/carbon/font.cpp

@@ -252,6 +252,9 @@ void wxFontRefData::Free()
 #endif
     m_cgFont.reset();
 #if wxOSX_USE_ATSU_TEXT
+#if wxOSX_USE_CARBON
+    m_macThemeFontID = kThemeCurrentPortFont ;
+#endif
     if ( m_macATSUStyle )
     {
         ::ATSUDisposeStyle((ATSUStyle)m_macATSUStyle);