make sure native font exists, before asking about fixed width

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71810 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/carbon/font.cpp

@@ -742,8 +742,11 @@ wxSize wxFont::GetPixelSize() const
 
 bool wxFont::IsFixedWidth() const
 {
-    wxCHECK_MSG( M_FONTDATA != NULL , wxFONTWEIGHT_MAX, wxT("invalid font") );
+    wxCHECK_MSG( M_FONTDATA != NULL , false, wxT("invalid font") );
     
+    // cast away constness otherwise lazy font resolution is not possible
+    const_cast<wxFont *>(this)->RealizeResource();
+
     return M_FONTDATA->IsFixedWidth();
 }