Check for nullptr on getGlobalLinkTransform

[AdamPettinger]

Description

Checks for nullptr when looking up a link transformation. The LinkModel* is set as nullptr here if the link name isn't known. This PR makes it throw in this case, instead of Seg Faulting. This should probably be backported to Moveit1 as well

I found this by modifying this line to be an unknown frame, then running the servo teleop demo with keyboard (arrow keys) input

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

Merging #611 (22b4b05) into main (bf6357e) will increase coverage by 0.01%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##             main     #611      +/-   ##
==========================================
+ Coverage   46.96%   46.96%   +0.01%     
==========================================
  Files         185      185              
  Lines       19655    19659       +4     
==========================================
+ Hits         9229     9231       +2     
- Misses      10426    10428       +2     

Impacted Files	Coverage Δ
...bot_state/include/moveit/robot_state/robot_state.h	85.32% <50.00%> (-0.81%)	⬇️

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[tylerjw]

Thank you for fixing this. At some point we should add a test for this.

[AndyZe]

Good catch!

Are you sure you want to throw a std::runtime_error, though?

I don't see that done anywhere else in robot_state.h or robot_state.cpp. I think it should be like this, instead:

throw Exception("Invalid link");

To match what's done here.

[AdamPettinger]

Good catch!

Are you sure you want to throw a std::runtime_error, though?

I don't see that done anywhere else in robot_state.h or robot_state.cpp. I think it should be like this, instead:

throw Exception("Invalid link");

To match what's done here.

Seems good to me, switched over to that