I am creating a softphone using HTML and visualforce. Everything was working fine but suddenly I can't save my changes in developer's console.

When I checked the browser console, I see this error:

(/_ui/common/apex/debug/ApexCSIPage) Uncaught TypeError: Cannot read property 'codeEditor' of undefinedUncaught TypeError: Cannot read property 'codeEditor' of undefined

I don't have any error in my visualforce page. Nothing in developer console is saving.

Any idea what this is and how can i resolve it?