Your pastie link doesn’t work.
This is working for me:
$myslug = 'my-test-group';
if ( bp_has_groups('type=single-group&slug='.$myslug) )
For some reason, you have to add the type as “single-group” as well.
If you’re just trying to get the group avatar of one group… just use bp_group_avatar() (view the params in bp-groups-templatetags.php) or bp_core_fetch_avatar() (view params in bp-core-avatars.php).