Log when named target does not exist

[rcywongaa]

Description

This avoids hiding the (likely) bug where an incorrect state name is given

Replaces #1579

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

Base: 51.11% // Head: 51.10% // Decreases project coverage by -0.02% ⚠️

Coverage data is based on head (8e6c214) compared to base (e960047).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1580      +/-   ##
==========================================
- Coverage   51.11%   51.10%   -0.01%     
==========================================
  Files         380      380              
  Lines       31796    31796              
==========================================
- Hits        16250    16246       -4     
- Misses      15546    15550       +4     

Impacted Files	Coverage Δ
...nning_scene_monitor/src/planning_scene_monitor.cpp	45.29% <0.00%> (-0.43%)	⬇️

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[AndyZe]

Looks good to me. Thanks!

For future reviewers, here's the link to getVariableDefaultPositions:

https://github.com/ros-planning/moveit2/blob/e96004702bbd338a08340eab0985fd04c74968fa/moveit_core/robot_model/src/joint_model_group.cpp#L450

[henningkayser]

Makes sense to me, thank you!