Reduce the state_block_vector in case of one single state block

src/landmark/landmark_base.cpp

@@ -18,15 +18,16 @@ LandmarkBase::LandmarkBase(const std::string& _type, StateBlockPtr _p_ptr, State
         landmark_id_(++landmark_id_count_)
 {
     state_block_vec_[0] = _p_ptr;
-    state_block_vec_[1] = _o_ptr;
+    if (_o_ptr)
+        state_block_vec_[1] = _o_ptr;
+    else
+        state_block_vec_.resize(1);
 
-//    std::cout << "constructed  +L" << id() << std::endl;
 }
 
 LandmarkBase::~LandmarkBase()
 {
     removeStateBlocks();
-//    std::cout << "destructed   -L" << id() << std::endl;
 }
 
 void LandmarkBase::remove(bool viral_remove_empty_parent)