macro fix for Py2.4 in C++ mode

Cython/Utility/ModuleSetupCode.c

@@ -47,10 +47,10 @@
   #define PY_FORMAT_SIZE_T ""
   #define PyInt_FromSsize_t(z) PyInt_FromLong(z)
   #define PyInt_AsSsize_t(o)   __Pyx_PyInt_AsInt(o)
-  #define PyNumber_Index(o)    ((PyNumber_Check(o) && !PyFloat_Check(o)) ? \
-                                PyNumber_Int(o) \
-                                : (PyErr_Format(PyExc_TypeError, "expected index value, got %.200s", \
-                                                Py_TYPE(o)->tp_name), NULL))
+  #define PyNumber_Index(o)    ((PyNumber_Check(o) && !PyFloat_Check(o)) ? PyNumber_Int(o) : \
+                                (PyErr_Format(PyExc_TypeError, \
+                                              "expected index value, got %.200s", Py_TYPE(o)->tp_name), \
+                                 (PyObject*)0))
   #define PyIndex_Check(o)     (PyNumber_Check(o) && !PyFloat_Check(o) && !PyComplex_Check(o))
   #define PyErr_WarnEx(category, message, stacklevel) PyErr_Warn(category, message)
   #define __PYX_BUILD_PY_SSIZE_T "i"