- for(vector<TrackIter>::const_iterator i=unlinked_endpoints.begin(); i!=unlinked_endpoints.end(); ++i)
- if(extend_tracks.front()->link_to(**i))
- break;
+ if(!extend_tracks.empty())
+ {
+ for(vector<TrackIter>::const_iterator i=unlinked_endpoints.begin(); i!=unlinked_endpoints.end(); ++i)
+ if(extend_tracks.front()->link_to(**i))
+ break;
+ }