PYTHON-969 - Check return value from PyObject_Call before using it in PyObject_GetAttrString.

Author: Luke Lovett

bson/_cbsonmodule.c

@@ -1912,6 +1912,12 @@ static PyObject* get_value(PyObject* self, const char* buffer,
  }
  Py_XDECREF(utc_type);
  value = PyObject_Call(replace, args, kwargs);
+ if (!value) {
+ Py_DECREF(replace);
+ Py_DECREF(args);
+ Py_DECREF(kwargs);
+ goto invalid;
+ }
 
  /* convert to local time */
  if (options->tzinfo != Py_None) {