swig %typemap generated list typeerror

[txtoth]

I'm trying to map a security_contex t_t ** to a python list. After
calling the method that returns this type when I process the returned
list in a for loop I get:
TypeError: expected string or Unicode object, NoneType found
after processing the last list entry. Can anyone see what I'm doing
wrong? Do I need to do something else to the list to somehow terminate
it?

%typemap(argout ) security_contex t_t ** {
PyObject *list_security_ context = PyList_New(0); // Create the
list.
if (list_security_ context) {
security_contex t_t **p_p_security_ context_t = arg3;
while (*p_p_security_ context_t) { // Move each string
into the list.
security_contex t_t *p_security_con text_t =
*p_p_security_c ontext_t;
if (PyList_Append( list_security_c ontext,
PyString_FromSt ring((char
*)*p_security_c ontext_t)) < 0) {
fprintf(stderr, "Fail to insert item in
list.\n");
$result = -1;
break;
}
p_p_security_co ntext_t++;
}
}
else {
fprintf(stderr, "Fail to create list.\n");
$result = -1;
}

$result = SWIG_Python_App endOutput($resu lt,
list_security_c ontext);

}