"Download Project Source" broken in web editor

[ator-dev]

Godot version

4.0.stable

System information

Ubuntu 22.04.2 LTS, tested on Firefox and Chromium

Issue description

The web editor no longer allows downloading your project's source from Project > Tools > Download Project Source. This is a critical issue for the web since there is no other way to backup or move your projects, seeing as neither version control nor cloud backup is yet supported (something I am hoping to investigate in future). Every web editor project is essentially stuck in a virtual filesystem limbo.

Reintroduces #71702

Steps to reproduce

• Open the web editor at https://editor.godotengine.org/releases/4.0.1.stable/
• Create and open a new project, or open an existing one
• Go to Project > Tools > Download Project Source
• Check whether anything is downloaded, and look at the output - it should read:
  • not enough arguments for format string
  • Unable to create ZIP file.

Minimal reproduction project

Uploading a project to the web editor would be more effort that it's worth.

[ator-dev]

Just thought to look at devtools output. On pressing the button, it reads only:

USER ERROR: not enough arguments for format string
   at: vformat (./core/variant/variant.h:830)
USER ERROR: Unable to create ZIP file.
   at: _download_zip (platform/web/api/web_tools_editor_plugin.cpp:87)