Be a bit more correct in relation to strict aliasing rules

Author: Tolker-KU

pandas/_libs/src/vendored/ujson/python/objToJSON.c

@@ -381,13 +381,16 @@ static char *PyDecimalToUTF8Callback(JSOBJ _obj, JSONTypeContext *tc,
   Py_DECREF(format_spec);
 
   if (str == NULL) {
-    *len = 0;
     ((JSONObjectEncoder *)tc->encoder)->errorMsg = "";
     return NULL;
   }
 
   GET_TC(tc)->newObj = str;
-  char *outValue = (char *)PyUnicode_AsUTF8AndSize(str, (Py_ssize_t *)len);
+
+  Py_ssize_t s_len = 0;
+  char *outValue = (char *)PyUnicode_AsUTF8AndSize(str, &s_len);
+  *len = s_len;
+
   return outValue;
 }