gh-116296: Fix refleak in reduce_newobj() corner case (#116297)

Co-authored-by: Brandt Bucher <[email protected]>

Author: erlend-aasland

Misc/NEWS.d/next/Core and Builtins/2024-03-04-10-19-51.gh-issue-116296.gvtxyU.rst

@@ -0,0 +1 @@
+Fix possible refleak in :meth:`!object.__reduce__` internal error handling.

Objects/typeobject.c

@@ -6549,6 +6549,7 @@ reduce_newobj(PyObject *obj)
     }
     else {
         /* args == NULL */
+        Py_DECREF(copyreg);
         Py_DECREF(kwargs);
         PyErr_BadInternalCall();
         return NULL;