"Custom Purge URL" displays previous value.

[KirillGritcenko]

What's the bug?

"Custom Purge URL" displays previous value.

How to reproduce?

1. Open settings page;
2. Insert several url's in the "Custom Purge URL" textarea;
3. Click on "Save All Changes" button. After page reload, this field will be empty;
4. Insert another several url's;
5. Click on "Save All Changes" button. After page reload, you'll see url's you inserted on step 2.

Screenshots