[PlayerModel] [Fix] make timeFocusedAtMs thread safe

[jkasten2]

Description

One Line Summary

Fix rare null crash with timeFocusedAtMs by making it thread safe.

Details

Motivation

A few customers have seen a rare crash.

Scope

Only affects focus time calculations.

Crash Example

java.lang.NullPointerException: Attempt to invoke virtual method 'long java.lang.Long.longValue()' on a null object reference
  at com.onesignal.FocusTimeController.getTimeFocusedElapsed(FocusTimeController.java:98)
  at com.onesignal.FocusTimeController.appStopped(FocusTimeController.java:50)
  at com.onesignal.ActivityLifecycleHandler$1.run(ActivityLifecycleHandler.java:186)

Testing

Manual testing

Tested on an Android 14 emulator, ensuring the on_focus endpoint was called with the the correct time.

Affected code checklist

• Notifications
  • Display
  • Open
  • Push Processing
  • Confirm Deliveries
• Outcomes
• Sessions
• In-App Messaging
• REST API requests
• Public API changes

Checklist

Overview

• I have filled out all REQUIRED sections above
• PR does one thing
• 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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