OneSignal v1.17 creates Mixed Content error in browser console when saving draft

Hi,
I experience this bug. To figure out where it came from, I tried deactivating all plugins, and only keep OneSignal activated, and that’s how I determine that the error was produced by this plugin.

How to replicate?

1) Deactivate all plugins
2) Activate only OneSignal
3) Go to post
4) Select an existing post’s draft to edit
5) Make any modification on the page, and open your browser console
6) Click the button “Save Draft”

Result: A mixed content error HTTP/HTTPS appears, that blocks the content from being saved.

Side note :
– When the problem is not there, the edit page loads and it shows “Saved” (with cross checked)
– When problem arises due to your plugin installed, then it shows “Save Draft” instead.