Fatal error on activation

[brianhogg]

Reproduction Steps

1. Install version of LifterLMS before 7.5.0
2. Try to upgrade to the latest version (7.7.1)

Expected Behavior

Plugin activates without error

Actual Behavior

Uncaught Error: Call to a member function log() on null in /Users/jgarturo/Local Sites/dev/app/public/wp-content/plugins/lifterlms/includes/class-llms-db-ugrader.php:160

This issue has be recreated:

• Locally
• On a staging site
• On a production website
• With only LifterLMS and a default theme

[brianhogg]

Because we're running on the activation hook, need to initialize the background updater if it's not already.