What steps will reproduce the issue?
When going to take the screen capture, scroll down and try to take it by clicking on the lower parts of the webpage. This resulted in an error 'can't read property 'id' of null' and the screen capture was not taken.
What would you expect to be the outcome?
The screen capture should be taken no matter where the user clicked on the page.
All these details will help people to fix any potential bugs?
Pretty sure this issue is in overlayscreen.js as the error was coming from line 266