Blacklist: Avoid crash when dialog dismissed via back button.

A user usually presses the back button only
when he/she does not want the changes to be saved.
Hence we need to revert the changes that took place
when the dialog is dismissed with back button.

Change-Id: Ifa3ef41f02f11d1e1627071532d8f915e3b445b6
Automatic Translation Import

Change-Id: I37933742030c49132afdba0840291897ae280e50