User Agent: Mozilla/5.0 (X11; Linux i686; rv:64.0) Gecko/20100101 Firefox/64.0

Steps to reproduce:

1. Open two profiles (-no-remote)
2. Wait for Update or force manual update on one of them
3. Another one probably break because of updated files.

Actual results:

I use multiple profiles and usually I do not allow Firefox to update automatically.
I forgot to disable auto-update on one of the profiles and after update get installed another running profile broke. I was unable to change tabs, play videos and links opened in new tabs were empty. I had have to restart browser.

Problem is known for me for a long time. I was just too lazy to disable auto-update on one of my profiles.

Expected results:

Firefox should be able to check if another profile isn't working then show the alert and let safely close another instances to prevent data lose.