Issue #20515: Fix NULL pointer dereference introduced by issue #20368

CID 1167595

Misc/NEWS

@@ -45,6 +45,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #20515: Fix NULL pointer dereference introduced by issue #20368.
+
 - Issue #19186: Restore namespacing of expat symbols inside the pyexpat module.
 
 - Issue #20426: When passing the re.DEBUG flag, re.compile() displays the

Modules/_tkinter.c

@@ -1568,6 +1568,9 @@ varname_converter(PyObject *in, void *_out)
     if (PyUnicode_Check(in)) {
         Py_ssize_t size;
         s = PyUnicode_AsUTF8AndSize(in, &size);
+        if (s == NULL) {
+            return 0;
+        }
         if (size > INT_MAX) {
             PyErr_SetString(PyExc_OverflowError, "string is too long");
             return 0;