librpc/py_security: Don’t pass a NULL pointer to PyUnicode_FromString()

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

source4/librpc/ndr/py_security.c

@@ -310,6 +310,10 @@ static PyObject *py_descriptor_as_sddl(PyObject *self, PyObject *args)
 		sid = NULL;
 
 	text = sddl_encode(NULL, desc, sid);
+	if (text == NULL) {
+		PyErr_SetString(PyExc_ValueError, "Unable to encode SDDL");
+		return NULL;
+	}
 
 	ret = PyUnicode_FromString(text);