WIP: Resolve "std::set and std::map instead of std::list in wolf nodes"

Closes #213 (closed)

src/frame/frame_base.cpp

@@ -287,6 +287,7 @@ void FrameBase::link(TrajectoryBasePtr _trj_ptr)
 {
     assert(!is_removing_ && "linking a removed frame");
     assert(this->getTrajectory() == nullptr && "linking an already linked frame");
+    assert(isKey() && "Trying to link a non keyframe");
 
     if(_trj_ptr)
     {