UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.108 Safari/537.36

Steps to reproduce the problem:
1. Clear/reset browser settings
2. Find magnet link to open external program
3. Select "Always remember..." preference
4. Try link again

What is the expected behavior?
Preference made with original pop-up to be saved

What went wrong?
In Preferences JSON file, "protocol_handler":{"excluded_schemes":{}} is is not saving the preference selected. 

Did this work before? Yes Pre 63.0.3239.84

Chrome version: 63.0.3239.108  Channel: stable
OS Version: OS X 10.12.6
Flash Version: 28.0.0.126

This issue started with release 63.0.3239.84.

link to discussion:

https://productforums.google.com/forum/?utm_medium=email&utm_source=footer#!msg/chrome/xWmyJqVgRfk/Azlh8yeMCgAJ

Current work around is to manually enter excluded_scheme in empty brackets located in Preferences file. This will revert is browser is cleared/reset.