apply petr's comment

Author: shihai1991

Python/import.c

@@ -442,8 +442,8 @@ _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
     }
 
     // bpo-44050: Extensions and def->m_base.m_copy can be updated
-    // when extension module created from PyModule_Create().
-    if (_Py_IsMainInterpreter(tstate->interp) || def->m_slots == NULL) {
+    // when the extension module doesn't support sub-interpreters.
+    if (_Py_IsMainInterpreter(tstate->interp) || def->m_size == -1) {
         if (def->m_size == -1) {
             if (def->m_base.m_copy) {
                 /* Somebody already imported the module,