Don't try to remove the referrer from an empty page state

BUG=339790
R=marja@chromium.org

Review URL: https://codereview.chromium.org/166303003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251418 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251418