gh-101967: add a missing error check (GH-101968)

(cherry picked from commit 89413bb)

Co-authored-by: Eclips4 <[email protected]>

Author: miss-islington

Misc/NEWS.d/next/Core and Builtins/2023-02-16-23-19-01.gh-issue-101967.Kqr1dz.rst

@@ -0,0 +1 @@
+Fix possible segfault in ``positional_only_passed_as_keyword`` function, when new list created.

Python/ceval.c

@@ -4718,7 +4718,9 @@ positional_only_passed_as_keyword(PyThreadState *tstate, PyCodeObject *co,
 {
     int posonly_conflicts = 0;
     PyObject* posonly_names = PyList_New(0);
-
+    if (posonly_names == NULL) {
+        goto fail;
+    }
     for(int k=0; k < co->co_posonlyargcount; k++){
         PyObject* posonly_name = PyTuple_GET_ITEM(co->co_varnames, k);