fix(app): Avoid modifying the array when reading file URLs for browser downloads

[nellh]

Fixes issue #3232 caused by this array no longer being possible to modify in place.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 45.66%. Comparing base (4a5bf01) to head (dc6da53).
Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
...pp/src/scripts/dataset/download/download-native.js	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3234   +/-   ##
=======================================
  Coverage   45.66%   45.66%           
=======================================
  Files         595      595           
  Lines       38013    38013           
  Branches     1167     1167           
=======================================
  Hits        17357    17357           
  Misses      20459    20459           
  Partials      197      197           

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[sentry]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ TypeError: Failed to fetch /datasets/ds003871/versions/1.0.2 View Issue

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