Update bp_get_send_public_message_link() to use bp_get_displayed_user_username() rather than bp_core_get_username(). Also add a bp_is_user() check so that false is properly returned when there is no displayed user, and removes $bp global touch.

Avoids possible debug notice if function is used out of context.



git-svn-id: https://buddypress.svn.wordpress.org/trunk@7486 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Update phpdoc @uses for bp_get_send_public_message_link().

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7487 cdf35c40-ae34-48e0-9cc9-0c9da1808c22