mod_c2s_limit_sessions: Fix check when it's the first connection Creation of the sessions[username] entry happens after the "pre-resource-bind" event, before the "resource-bind" event. Thus, for a users first connection, it may not exist. This led to an 'attempt to index a nil value' error, fixed here.

module:depends("cloud_notify_encrypted");
module:depends("cloud_notify_priority_tag");
module:depends("cloud_notify_filters");