[BugFix] Improve Warning For Invalid Defaults Key In user_settings.json

[deeleeramone]

1. Why?:

   • Adds clarity and actionable information to the warning.

2. What? (1-3 sentences or a bullet point list):

   • Suppressed if "routes" is actually empty and/or when show_warnings is set to false.

3. Impact:

   • Annoying warning will no longer display if the user happens to have a legacy user_settings.json file with this key.
   • The warning will be broadcast only when routes is actually populated

4. Testing Done:

   • Play around with user_settings.json to show and suppress the warning.