Regex Search Not Responding

[WORMSS]

I was doing a Find and Replace In Files (well, just the Find).
Whole Word unticked
Match case unticked
Escaped characters unticked
Regular expression ticked
Look in subdirectories ticked
Look in comments unticked
Look in strings unticked.

Find What: ^}(?!;)
Extension Filter *.js

This should find all } that are the first char on the line, and is not followed by a ;
FD got ¼ way through the search (by indication of green bar at bottom of page) and then became Not Responding. Cancel button wouldn't work and I had to force close.