Fix code linting issue where a slice was created non-empty and appended-to

[mna]

#19290

Checklist for submitter

• Changes file added for user-visible changes in changes/, orbit/changes/ or ee/fleetd-chrome/changes.
  See Changes files for more information.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.24%. Comparing base (0265554) to head (4b3f325).
Report is 64 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #19490       +/-   ##
===========================================
- Coverage   69.81%   63.24%    -6.58%     
===========================================
  Files          15      984      +969     
  Lines         921   120590   +119669     
  Branches       75       75               
===========================================
+ Hits          643    76266    +75623     
- Misses        277    38125    +37848     
- Partials        1     6199     +6198     

Flag	Coverage Δ
backend	63.19% <100.00%> (?)

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