R1:101ce834b8ad

Fix PHP 8.1 strlen() error when database replication Seconds_Behind_Master is NULL

Summary:
When MySQL database replication is configured, but not running, the slave status Seconds_Behind_Master is NULL.
When this value is passed to strlen() an error is thrown.

Fixes T15507

Test Plan:
* Configure database replication such that Seconds_Behind_Master is NULL
* Restart php-fpm
* Go to Phorge web site.

Reviewers: O1 Blessed Committers, chris

Reviewed By: O1 Blessed Committers, chris

Subscribers: speck…