Due to the way grackle is written, need to update grackle_data before calling a grackle function

src/cooling_wrapper.c

@@ -99,6 +99,10 @@ PyArrayObject* pycooling_rate(PyObject* self, PyObject* args) {
 
   struct part p;
 
+#ifdef COOLING_GRACKLE
+  grackle_data = &cooling->chemistry;
+#endif
+
   /* return object */
   PyArrayObject *rate = PyArray_NewLikeArray(energy, NPY_ANYORDER, NULL, 1);