_PyStack_UnpackDict() now returns -1 on error

Issue #29286. Change _PyStack_UnpackDict() prototype to be able to notify of
failure when args is NULL.
diff --git a/Objects/methodobject.c b/Objects/methodobject.c
index 1e9ad0d..7bff6a0 100644
--- a/Objects/methodobject.c
+++ b/Objects/methodobject.c
@@ -240,8 +240,8 @@
         PyObject *kwnames;
         _PyCFunctionFast fastmeth = (_PyCFunctionFast)meth;
 
-        stack = _PyStack_UnpackDict(args, nargs, kwargs, &kwnames, func_obj);
-        if (stack == NULL) {
+        if (_PyStack_UnpackDict(args, nargs, kwargs,
+                                &stack, &kwnames, func_obj) < 0) {
             return NULL;
         }