file: and allow-empty: do not work together

When I use this:

        file: coverage.xml
        allow-empty: true

Then, I get this output:

Run coveralls report    --allow-empty   coverage.xml 
 
⠀⠀⠀⠀⠀⠀⣿
⠀⠀⠀⠀⠀⣼⣿⣧⠀⠀⠀⠀⠀⠀⠀ ⣠⣶⣾⣿⡇⢀⣴⣾⣿⣷⣆ ⣿⣿⠀⣰⣿⡟⢸⣿⣿⣿⡇ ⣿⣿⣿⣷⣦⠀⠀⢠⣿⣿⣿⠀⠀⣿⣿⠁⠀⣼⣿⡇⠀⢀⣴⣾⣿⡷
⠶⣶⣶⣶⣾⣿⣿⣿⣷⣶⣶⣶⠶  ⣸⣿⡟ ⠀⢠⣿⣿⠃⠈⣿⣿⠀⣿⣿⢠⣿⡿⠀⣿⣿⣧⣤⠀⢸⣿⡇⣠⣿⡿⠀⢠⣿⡟⣿⣿⠀⢸⣿⡿⠀⠀⣿⣿⠃⠀⢸⣿⣧⣄
⠀⠀⠙⢻⣿⣿⣿⣿⣿⡟⠋⠁⠀⠀ ⣿⣿⡇⠀ ⢸⣿⣿⠀⣸⣿⡟⠀⣿⣿⣾⡿⠁ ⣿⣿⠛⠛⠀⣿⣿⢿⣿⣏⠀⢀⣿⣿⣁⣿⣿⠀⣾⣿⡇⠀⢸⣿⡿⠀⠀⡀⠙⣿⣿⡆
⠀⠀⢠⣿⣿⣿⠿⣿⣿⣿⡄⠀⠀⠀ ⠙⢿⣿⣿⠇⠈⠿⣿⣿⡿⠋⠀⠀⢿⣿⡿⠁⠀⢸⣿⣿⣿⡇⢸⣿⣿⠀⣿⣿⣄⣾⣿⠛⠛⣿⣿⢠⣿⣿⣿ ⣼⣿⣿⣿ ⣿⣿⡿⠋⠀
⠀⢀⣾⠟⠋⠀⠀⠀⠙⠻⣷⡀⠀⠀
 
  v0.6.12

🚨 ERROR: Couldn't find specified file: coverage.xml
Error: Process completed with exit code 1.

See https://github.com/collective/icalendar/actions/runs/9751607002/job/26913556374?pr=678

I would expect that this would fail without an error as I set allow-empty: true.

Commit: https://github.com/collective/icalendar/pull/678/commits/f40d44b07783f8d6e490bb0589be40c8e3643820

Start by tracing how the GitHub Action constructs the Coveralls command from the file and allow-empty options, then reproduce the configuration shown in the issue. Done means a missing coverage.xml is accepted when allow-empty is true, while the same missing file still fails without that option.