"At a Glance" widget: Move `get_avatar()` line out of if-block.

This allows you to show avatars for custom comment types via the `get_avatar_comment_types` filter.

props zodiac1978.
fixes #26944.

git-svn-id: https://develop.svn.wordpress.org/trunk@27384 602fd350-edb4-49c9-b593-d223f7449a82