groups_update_last_activity() setup wrong

[dwenaus]

I saw a plugin that hooked into the groups_update_last_activity() function, (line 1355 in bp-groups.php) which accepts a group_id, however if you don't pass it a group_id, which is the case for actions, then the function does not look up the default id from $bp. The action hooks below it also probably don't work, and are therefore perhaps redundant.

If I'm correct I suggest fixing this function by adding some code that sets the group_id to the current group if one is not passed.

[boonebgorges]

(In [3319]) Sets default value of group_id in groups_update_last_activity() to current group id if no parameter is passed. Fixes #2536.