labwc: fix pipemenu and icon generation and not manage file

[LesVu]

Description

fix pipemenu and icon generation in menu.xml generator
and not manage file when user not define any option related to the file

Checklist

• Change is backwards compatible.

• Code formatted with nix fmt or
  nix-shell -p treefmt nixfmt-rfc-style keep-sorted --run treefmt.

• Code tested through nix-shell --pure tests -A run.all
  or nix build --reference-lock-file flake.lock ./tests#test-all using Flakes.

• Test cases updated/added. See example.

• Commit messages are formatted like

  {component}: {description}
  
  {long description}
  

  See CONTRIBUTING for more information and recent commit messages for examples.

• If this PR adds a new module

  • Added myself as module maintainer. See example.

Maintainer CC