Add default value to legacy notification types

[jinliu9508]

Description

One Line Summary

Add default value to legacy notification types

Details

Motivation

Fix a bug that causes a "value not found" exception when trying to read the value of notification_types from the legacy user json string.

Testing

This PR contains 3 commits. The first commit simulates a crash scenario whose error track is identical from that reported by other users. The second commit applies a fix that prevents the crash. And the third commit is the final code change.

Other

It appears that this issue occurs only on devices that already have a legacy player ID. In the event that such a scenario persists after this fix, the corrupted push subscription will be opted in with a status of NO_PERMISSION.

Checklist

Overview

• I have filled out all REQUIRED sections above
• PR does one thing
  • If it is hard to explain how any codes changes are related to each other then it most likely needs to be more than one PR
• Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• I have included test coverage for these changes, or explained why they are not needed
• All automated tests pass, or I explained why that is not possible
• I have personally tested this on my device, or explained why that is not possible

Final pass

• Code is as readable as possible.
  • Simplify with less code, followed by splitting up code into well named functions and variables, followed by adding comments to the code.
• I have reviewed this PR myself, ensuring it meets each checklist item
  • WIP (Work In Progress) is ok, but explain what is still in progress and what you would like feedback on. Start the PR title with "WIP" to indicate this.

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This change is 

[jkasten2]

Please add details to the PR of how this was tested

[jkasten2]

LGTM! Thanks for testing to confirm the fix