No free derivative variables

[Tfly6]

I built a trajectory generator based on example_planner.cpp for PX4 SITL, but it throws this error when running

WARNING: Logging before InitGoogleLogging() is written to STDERR
W0403 21:18:40.516448  7140 polynomial_optimization_linear_impl.h:344] No free constraints set in the vertices. Polynomial can not be optimized. Outputting fully constrained polynomial.
W0403 21:18:40.516664  7140 polynomial_optimization_nonlinear_impl.h:421] No free derivative variables, same as time-only optimization.

How do I solve this problem?

[Tfly6]

I referred to uav_motion/src/trajectory_generator.cpp at master · ZhiangChen/uav_motion and changed

start.makeStartOrEnd(current_pose_.translation(), derivative_to_optimize);

to

start.addConstraint(mav_trajectory_generation::derivative_order::POSITION, current_pose_.translation());

Although the error has been resolved, I don't know why.
can you help me ? thank you very much!