[lipstick] Fix notification category update
[lipstick] Fix notification category update

Do not modify the hash of notifications while traversing the hash.

giucam/lipstick,pvuorela/lipstick,sletta/lipstick,pvuorela/lipstick,sletta/lipstick,giucam/lipstick,giucam/lipstick,pvuorela/lipstick,sletta/lipstick