tweak try/catch again

src/deluge_core.cpp

@@ -1802,11 +1802,11 @@ static PyObject *torrent_replace_trackers(PyObject *self, PyObject *args)
   const char* tracker;
   if (!PyArg_ParseTuple(args, "iz", &unique_ID, &tracker))
     return NULL;
+
+  try {
       long index = get_index_from_unique_ID(unique_ID);
       if (PyErr_Occurred())
         return NULL;
-
-  try {
       if (M_torrents->at(index).handle.is_valid()){
         std::vector<libtorrent::announce_entry> trackerlist;
         std::istringstream trackers(tracker);