Avoid C compiler warning when refnanny is not used.

Cython/Utility/ObjectHandling.c

@@ -2563,12 +2563,16 @@ static PyObject *__Pyx_PyMethod_New(PyObject *func, PyObject *self, CYTHON_UNUSE
     #if CYTHON_REFNANNY
         #define __Pyx_PyUnicode_ConcatInPlace(left, right) __Pyx_PyUnicode_ConcatInPlaceImpl(&left, right, __pyx_refnanny)
     #else
-        #define __Pyx_PyUnicode_ConcatInPlace(left, right) __Pyx_PyUnicode_ConcatInPlaceImpl(&left, right, NULL)
+        #define __Pyx_PyUnicode_ConcatInPlace(left, right) __Pyx_PyUnicode_ConcatInPlaceImpl(&left, right)
     #endif
     // __Pyx_PyUnicode_ConcatInPlace is slightly odd because it has the potential to modify the input
     // argument (but only in cases where no user should notice). Therefore, it needs to keep Cython's
     // refnanny informed.
-    static CYTHON_INLINE PyObject *__Pyx_PyUnicode_ConcatInPlaceImpl(PyObject **p_left, PyObject *right, void* __pyx_refnanny); /* proto */
+    static CYTHON_INLINE PyObject *__Pyx_PyUnicode_ConcatInPlaceImpl(PyObject **p_left, PyObject *right
+        #if CYTHON_REFNANNY
+        , void* __pyx_refnanny
+        #endif
+    ); /* proto */
 #else
 #define __Pyx_PyUnicode_ConcatInPlace __Pyx_PyUnicode_Concat
 #endif
@@ -2595,7 +2599,11 @@ __Pyx_unicode_modifiable(PyObject *unicode)
     return 1;
 }
 
-static CYTHON_INLINE PyObject *__Pyx_PyUnicode_ConcatInPlaceImpl(PyObject **p_left, PyObject *right, void* __pyx_refnanny) {
+static CYTHON_INLINE PyObject *__Pyx_PyUnicode_ConcatInPlaceImpl(PyObject **p_left, PyObject *right
+        #if CYTHON_REFNANNY
+        , void* __pyx_refnanny
+        #endif
+    ) {
     // heavily based on PyUnicode_Append
     PyObject *left = *p_left;
     Py_ssize_t left_len, right_len, new_len;