Codecheck fixes

[scpeters]

🦟 Bug fix

Fixes some make codecheck issues with newer cppcheck

Summary

There are a few issues printed by make codecheck without generating a failure. I noticed this on macOS, which has a newer cppcheck from brew. I've fixed a few of those complaints here:

• 65dfd6f: pass by const reference in more places
• e955699: remove unused variable
• dcf1422: simplify redundant logic. There are a few places where we return early if a pointer is nullptr, but we continue to check its value. This eliminates those redundant checks, and moves an unreachable console error message to the appropriate place.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge

[codecov-commenter]

Codecov Report

Merging #730 (dcf1422) into sdf11 (bf3cbef) will increase coverage by 0.02%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##            sdf11     #730      +/-   ##
==========================================
+ Coverage   88.09%   88.12%   +0.02%     
==========================================
  Files          73       73              
  Lines       11030    11023       -7     
==========================================
- Hits         9717     9714       -3     
+ Misses       1313     1309       -4     

Impacted Files	Coverage Δ
src/FrameSemantics.cc	73.90% <ø> (+0.02%)	⬆️
src/parser.cc	85.46% <71.42%> (+0.22%)	⬆️
src/Converter.cc	93.19% <100.00%> (ø)

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[chapulina]

Nice! We could change make codecheck to run on Focal instead of Bionic, which I think should help catching more like this in the future.

[scpeters]

Nice! We could change make codecheck to run on Focal instead of Bionic, which I think should help catching more like this in the future.

that would be nice to parameterize so packages can opt-in when they are ready

[osrf-triage]

This pull request has been mentioned on Gazebo Community. There might be relevant details there:

https://community.gazebosim.org/t/new-ignition-releases-2022-03-25-fortress-edifice-citadel/1343/1