I can't access the options in the theme editor.

Please could you clear your browser cache and try it again? Im having no issues this end, and I suspect you may be having cache issues from prior to the upgrade. Also please try clearing cache in the admin CP. If either of those work, let us know which.

If the above doesnt, let me know which browser and OS you are on

Thank you! Clearing browser cache did not work. Clear System Cache worked. 🙂 

Thank you for letting us know. I saw similar on mine, which is why I asked which cache worked. I have logged that as a bug, even if the initial issue isnt actually a bug there