Unexpected error when creating lessons without parent course.

[dominiquemariano]

Reproduction Steps

1. Start with a fresh install of WordPress and LifterLMS.
2. Go to WordPress Dashboard > Courses > Lessons and create a new lesson by clicking on the Add Lesson button.
3. Click on the LifterLMS button in this screenshot.
4. Click on the Settings button in this screenshot.
5. You'll get a popup saying "The editor has encountered an unexpected error.", as you can see in this screenshot.

Expected Behavior

Should not get the error in this screenshot.

Actual Behavior

The user is getting the error in this screenshot.

This issue has be recreated:

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

[brianhogg]

Related to support thread https://wordpress.org/support/topic/javascript-error-while-trying-to-enter-add-form-dashboard-page/