Detail

When set proxy to `OS default`, the `http.proxy` config of Git was set to `http.proxy=http://www.google.com:80`.

Steps to reproduce

1. Set proxy in Tool - Options
2. `git config --global -l` and here's the right proxy config `http.proxy=http://127.0.0.1:1080`
3. Clear proxy in Tool - Options (set to `OS default`)
4. `git config --global -l` and here's `http.proxy=http://www.google.com:80`.

Reproduced in v3.4.6.