If we have no error string, place None in the tuple.

Be more defensive about what we get back from the _isys module.  Do
not assume we get an error string.  If it's empty, place None in the
tuple.

1 files changed, 8 insertions, 1 deletions

diff --git a/isys/isys.c b/isys/isys.c
index 0813e5054..65ee688b3 100644
--- a/isys/isys.c
+++ b/isys/isys.c
@@ -291,7 +291,14 @@ static PyObject * doMount(PyObject * s, PyObject * args) {
         PyObject *tuple = PyTuple_New(2);
 
         PyTuple_SetItem(tuple, 0, PyInt_FromLong(rc));
-        PyTuple_SetItem(tuple, 1, PyString_FromString(err));
+
+        if (err == NULL) {
+            Py_INCREF(Py_None);
+            PyTuple_SetItem(tuple, 1, Py_None);
+        } else {
+            PyTuple_SetItem(tuple, 1, PyString_FromString(err));
+        }
+
         PyErr_SetObject(PyExc_SystemError, tuple);
     }