FitPeaks - fixing check to be start/stop

[peterfpeterson]

This was pointed out in #35837 and apparently by cppcheck (which was suppressed).

There is no associated issue.

Further detail of work

To test:

A code review is probably the best way to verify this.

This does not require release notes because nothing appears to set only one of the values.

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[MohamedAlmaki]

LGTM, just a small issue that's been hidden by a CPP suppression