Safe Browsing Back to safety button opens about:blank

[btlechowski]

Steps to Reproduce

1. Verify the *.store files have been created in <UserData>/Safe Browsing directory (on windows \AppData\Local\BraveSoftware\Safe Browsing)
   1a. If they are not then browse internet for few minutes till they are created
2. Open https://testsafebrowsing.appspot.com/
3. Open Should show a phishing warning in new tab
4. Click Back to safety button

Actual result:

about:blank page is opened

Expected result:

New tab is opened

Reproduces how often:

always

Brave version (chrome://version info)

Brave	0.55.5 Chromium: 70.0.3538.16 (Official Build) dev (64-bit)
Revision	16ed95b41bb05e565b11fb66ac33c660b721f778-refs/branch-heads/3538@{#306}
OS	Windows 7

cc @jumde

[btlechowski]

Same behavior as in Chrome. Closing. Sorry for the unnecessary notifications.