Copy content fails if running in a scheduled job

Description

Steps to reproduce
1. Create a scheduled job named "ExampleScheduledJob".
2. Build the project, and start the application.
3. Go to Admin > Admin > Scheduled Jobs.
4. Chose the "ExampleScheduledJob" and click the "Start Manually" button.

Expected:
Can copy the content successfully.

Actual:
Throw an exception "Object reference not set to an instance of an object" in the history tab and the log file.