Command final waypoint identically when traj_point_active_ptr_ is null

[egordon]

Addresses #671

Redux of #672 fix sent directly to master.
Requesting a back-port to humble if possible, as this seems to fix a bug noticed by anybody using closed-loop velocity or effort hardware control.

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 36.53%. Comparing base (e7f9962) to head (6919f38).
Report is 563 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #682      +/-   ##
==========================================
+ Coverage   35.78%   36.53%   +0.75%     
==========================================
  Files         189        7     -182     
  Lines       17570      676   -16894     
  Branches    11592      357   -11235     
==========================================
- Hits         6287      247    -6040     
+ Misses        994      134     -860     
+ Partials    10289      295    -9994     

Flag	Coverage Δ
unittests	36.53% <ø> (+0.75%)	⬆️

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see 194 files with indirect coverage changes