Don't duplicate categories when unlisting

op !== operation in all iterations of this loop except the first,
and using information from one operation to apply another one
doesn't work very well.

The fact that undefined cast to a number is NaN rather than 0
is very unhelpful :(

Also fixed some commas that should be semicolons.

Bug: 52238
Change-Id: I4138c023c955f2866881084506e24bb8b6db5a4d
Merge "Don't duplicate categories when unlisting"