Selecting exam lab when creating a lab, does not imply sign off intervals

Summary

Whenever the option exam lab is selected when creating a new lab, the checkbox of sign off intervals is not necessarily checked. And when trying to create a lab it does not give a message to indicate what is wrong.

Steps to reproduce

1. Create a new lab
2. Check off exam lab, but not sign off intervals
3. Press create lab

Possible Fix

• Automatically select the sign off intervals checkbox whenever exam lab is checked (make it dependent on exam lab checkbox)
• Show a redirect message whenever sign off intervals is not selected.