fix

Author: corona10

Objects/typeobject.c

@@ -1290,7 +1290,7 @@ _PyType_AllocNoTrack(PyTypeObject *type, Py_ssize_t nitems)
 {
     PyObject *obj;
     size_t extra = 0;
-    if (type->tp_flags & Py_TPFLAGS_TYPE_SUBCLASS) {
+    if (type->tp_flags & Py_TPFLAGS_TYPE_SUBCLASS || type->tp_vectorcall != NULL) {
         /* note that we need to add one, for the sentinel */
         extra = 1;
     }
@@ -1312,7 +1312,7 @@ _PyType_AllocNoTrack(PyTypeObject *type, Py_ssize_t nitems)
         _PyObject_Init(obj, type);
     }
     else {
-        _PyObject_InitVar((PyVarObject *)obj, type, nitems);
+        _PyObject_InitVar((PyVarObject *)obj, type, nitems + extra);
     }
     return obj;
 }