Fix e2e-widget.js for the case without flight argument

[romanlutz]

Description

Recently, e2e-widget.js was updated to allow for passing flights via -f. This works either with or without args for -f as it's used by the GitHub workflow. However, users can just as well call the script without -f at all. Currently, this leads to an error as we're calling .toString() on the argument which would be undefined. This change ensures that we don't do that while still mapping both cases of not specifying flights (either with -f and no extra args, or without -f) to flights as undefined.

Checklist

• I have added screenshots above for all UI changes.
• I have added e2e tests for all UI changes.
• Documentation was updated if it was needed.

[codecov-commenter]

Codecov Report

Merging #1529 (98b8ec9) into main (0a4f296) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1529   +/-   ##
=======================================
  Coverage   87.27%   87.27%           
=======================================
  Files         108      108           
  Lines        5108     5108           
=======================================
  Hits         4458     4458           
  Misses        650      650           

Flag	Coverage Δ
unittests	87.27% <ø> (ø)

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[github-actions]

https://responsibleai.blob.core.windows.net/pullrequest/microsoft/responsible-ai-toolbox/romanlutz/fix_e2e_widget_script/dashboard/index.html