[3.7] Fix a possible crash due to PyType_FromSpecWithBases() (GH-10304)

If the PyObject_MALLOC() call failed in PyType_FromSpecWithBases(),
PyObject_Free() would be called on a static string in type_dealloc().
(cherry picked from commit 0613c1e)

Co-authored-by: Zackery Spytz <[email protected]>

Author: ZackerySpytz

Objects/typeobject.c

@@ -2938,6 +2938,7 @@ PyType_FromSpecWithBases(PyType_Spec *spec, PyObject *bases)
             size_t len = strlen(old_doc)+1;
             char *tp_doc = PyObject_MALLOC(len);
             if (tp_doc == NULL) {
+                type->tp_doc = NULL;
                 PyErr_NoMemory();
                 goto fail;
             }