PHP Warning: Undefined array key “is_running” #614

Describe the bug
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Warnings in the debug log when a backup is running.

To Reproduce
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1. using 1.16.8 of Total Upkeep
2. Turn on debugging on WordPress
3. Check debug.log after running a backup

Expected behavior
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Screenshots
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[16-Feb-2025 21:15:46 UTC] PHP Warning: Undefined array key “is_running” in /volume1/web_packages/wordpress/wp-content/plugins/boldgrid-backup/admin/class-boldgrid-backup-admin-in-progress.php on line 508
[16-Feb-2025 21:15:51 UTC] PHP Warning: Undefined array key “is_running” in /volume1/web_packages/wordpress/wp-content/plugins/boldgrid-backup/admin/class-boldgrid-backup-admin-in-progress.php on line 508
[16-Feb-2025 21:15:56 UTC] PHP Warning: Undefined array key “is_running” in /volume1/web_packages/wordpress/wp-content/plugins/boldgrid-backup/admin/class-boldgrid-backup-admin-in-progress.php on line 508
[16-Feb-2025 21:16:01 UTC] PHP Warning: Undefined array key “is_running” in /volume1/web_packages/wordpress/wp-content/plugins/boldgrid-backup/admin/class-boldgrid-backup-admin-in-progress.php on line 508
[16-Feb-2025 21:16:06 UTC] PHP Warning: Undefined array key “is_running” in /volume1/web_packages/wordpress/wp-content/plugins/boldgrid-backup/admin/class-boldgrid-backup-admin-in-progress.php on line 508
[16-Feb-2025 21:16:11 UTC] PHP Warning: Undefined array key “is_running” in /volume1/web_packages/wordpress/wp-content/plugins/boldgrid-backup/admin/class-boldgrid-backup-admin-in-progress.php on line 508

Additional context
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