message: Spin: make visitCandidates() method const
diff: @@ -514,7 +514,7 @@ public:
  }
  template <typename FuncType>
  - void visitCandidates(const SpacePoint& pt, const FuncType&& candidatePredicate)
  + void visitCandidates(const SpacePoint& pt, FuncType&& candidatePredicate) const
  {
  if(!m_bb.contains(pt)) return;
  