Use is_user_logged_in(), have_comments in Theme's comments.php

[zeo]

is_user_logged_in() should be use instead of $user_ID in Theme's classic and default comments.php.

Use have_comments() instead of $comments in Classic theme comments.php

[ryan]

(In [11067]) Use is_user_logged_in(), have_comments in bundled themes. Props zeo. fixes #9626