Do not set the user's avatar image to a stub twice in a row

This CL contains a small clean-up missed in CL 136763003. The user avatar
image is needlessly being set to a stub twice in a row.

BUG=331365
TEST=None

Review URL: https://codereview.chromium.org/134423005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245911 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245911