Fix elevator system crash when empty laser scan msg is received.

[iche033]

🦟 Bug fix

Fixes #2531

Summary

See #2531 for instructions on reproducing the crash.

Added a check for non-empty laser scan ranges before accessing the elements.

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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