Fix uninitialized element used in mppi trajectory test

[mini-1235]

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Basic Info

Info	Please fill out this column
Ticket(s) this addresses	#4934
Primary OS tested on	Ubuntu
Robotic platform tested on
Does this PR contain AI generated software?	No

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Description of contribution in a few bullet points

• Fix bug as described in the issue

Description of documentation updates required from your changes

Description of how this change was tested

Unit test run around 10000 rounds, no error occured

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Future work that may be required in bullet points

For Maintainers:

• Check that any new parameters added are updated in docs.nav2.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

All modified and coverable lines are covered by tests ✅

see 2 files with indirect coverage changes

[SteveMacenski]

I see a few PRs from you over the last couple of weeks. First off, thanks! I’ll be getting to them all this week. I was out of town for a wedding the last 2 weeks and flying back home as we speak. Thanks for your patience.

[mini-1235]

I see a few PRs from you over the last couple of weeks. First off, thanks! I’ll be getting to them all this week. I was out of town for a wedding the last 2 weeks and flying back home as we speak. Thanks for your patience.

No worries at all! I really appreciate you taking the time to review them