Do not materialize an empty instance dict in BytesIO/StringIO.__getstate__

Check _PyObject_IsInstanceDictEmpty() first, as object.__getstate__() does,
instead of creating an empty dict just to find out that it is empty.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Author: eendebakpt

Modules/_io/bytesio.c

@@ -971,15 +971,15 @@ _io_BytesIO___getstate___impl(bytesio *self)
 
     if (initvalue == NULL)
         return NULL;
-    dict = PyObject_GenericGetDict((PyObject *)self, NULL);
-    if (dict == NULL) {
-        Py_DECREF(initvalue);
-        return NULL;
-    }
-    if (PyDict_GET_SIZE(dict) == 0) {
-        Py_SETREF(dict, Py_NewRef(Py_None));
+    if (_PyObject_IsInstanceDictEmpty((PyObject *)self)) {
+        dict = Py_NewRef(Py_None);
     }
     else {
+        dict = PyObject_GenericGetDict((PyObject *)self, NULL);
+        if (dict == NULL) {
+            Py_DECREF(initvalue);
+            return NULL;
+        }
         Py_SETREF(dict, PyDict_Copy(dict));
         if (dict == NULL) {
             Py_DECREF(initvalue);

Modules/_io/stringio.c

@@ -927,15 +927,15 @@ _io_StringIO___getstate___impl(stringio *self)
 
     if (initvalue == NULL)
         return NULL;
-    dict = PyObject_GenericGetDict((PyObject *)self, NULL);
-    if (dict == NULL) {
-        Py_DECREF(initvalue);
-        return NULL;
-    }
-    if (PyDict_GET_SIZE(dict) == 0) {
-        Py_SETREF(dict, Py_NewRef(Py_None));
+    if (_PyObject_IsInstanceDictEmpty((PyObject *)self)) {
+        dict = Py_NewRef(Py_None);
     }
     else {
+        dict = PyObject_GenericGetDict((PyObject *)self, NULL);
+        if (dict == NULL) {
+            Py_DECREF(initvalue);
+            return NULL;
+        }
         Py_SETREF(dict, PyDict_Copy(dict));
         if (dict == NULL) {
             Py_DECREF(initvalue);