Fix calling GpuRays::Destroy more than once

[iche033]

🦟 Bug fix

Summary

Fixes gz-sensors' INTEGRATION_dvl test with ogre on Harmonic

The test has been failing (crashing) on homebrew CI which runs test with ogre. I was able to reproduce the crash and found that the issue is due to the ogre node being destroyed twice on the rendering side. Added a check to make sure we return from the Destroy function if camera is null (indicates resources have been removed already). The same check exists in the ogre2 version.

To reproduce the test failure in Harmonic workspace:

RENDER_ENGINE_VALUES=ogre ./build/gz-sensors8/bin/INTEGRATION_dvl

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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[codecov]

Codecov Report

Merging #860 (93e7199) into main (5c78bd5) will not change coverage.
The diff coverage is n/a.

❗ Current head 93e7199 differs from pull request most recent head 65c739c. Consider uploading reports for the commit 65c739c to get more accurate results

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##             main     #860   +/-   ##
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  Coverage   75.02%   75.02%           
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  Files         183      183           
  Lines       16311    16311           
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  Hits        12237    12237           
  Misses       4074     4074