Set missing variable in BP_Groups_Group test

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7573 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Support more liberal params for disabling comments in bp_has_activities()

The 'display_comments' argument of bp_has_activities() takes either a string
value (such as 'threaded') or a bool false to disable comments altogether.
However, the false check in the query method is strict, meaning that various
analogous null values for display_comments were not recognized. In particular,
the strict check made it impossible to disable activity comments via a
querystring, as is often done in templates: ?display_comments=0.

This changeset adds 0, '0', 'false', and 'none' to the possible values for
the null display_comments value, to support the longtime codex suggestions.
Changes are made at the level of bp_has_activities(), which means that the
query method still requires a string false for $display_comments.

Fixes #5029

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7574 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Pinking shears

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7575 cdf35c40-ae34-48e0-9cc9-0c9da1808c22