Prevent a possible segmentation fault (#4141)

[jonipol]

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Basic Info

Info	Please fill out this column
Ticket(s) this addresses	#4141
Primary OS tested on	Ubuntu
Robotic platform tested on	Gazebo simulation of a Robauta robot
Does this PR contain AI generated software?	No

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Description of contribution in a few bullet points

• Prevent a possible segmentation fault in analytic_expansion at smac_planner

Defensive approach as Steve recommended in his comment on the issue. Added check if the iterator == vector.end(), as dereferencing that can lead into undefined behavior (appeared as segmentation fault in my case). Also added an early return for the case in which the vector would end up being empty, thus leading into the check previously mentioned.

Description of documentation updates required from your changes

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Future work that may be required in bullet points

For Maintainers:

• Check that any new parameters added are updated in navigation.ros.org
• Check that any significant change is added to the migration guide
• Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• Check that any new functions have Doxygen added
• Check that any new features have test coverage
• Check that any new plugins is added to the plugins page
• If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 90.12%. Comparing base (865fd32) to head (17b12ec).

❗ Current head 17b12ec differs from pull request most recent head 42393d3. Consider uploading reports for the commit 42393d3 to get more accurate results

Files	Patch %	Lines
nav2_smac_planner/src/analytic_expansion.cpp	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4147      +/-   ##
==========================================
+ Coverage   89.85%   90.12%   +0.26%     
==========================================
  Files         432      432              
  Lines       19406    19408       +2     
==========================================
+ Hits        17438    17492      +54     
+ Misses       1968     1916      -52     

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[SteveMacenski]

LGTM, just a small detail for branching

[SteveMacenski]

Add it to the if statement above

if (d > _search_info.analytic_expansion_max_length || d < sqrt_2) {

[SteveMacenski]

^ that would require moving the sqrt_2 definition above as well

[jonipol]

Thanks for feedback!

[SteveMacenski]

Mergify backporting failed, will need to be done manually