Got a Error after editing the lesson

I just submitted the Support Ticket for course error issue.

I think this issue would be critically issues for Fluent Community users. I just set up the New course, and then created the section and lesson under the section. So then, editing the each lesson detailed but I couldn't access this course with attached error message.

Please let me know how to fix by myself or fix it I'm not sure if it was bug or not.