[polari/wip/raresv/popoverRebasedOnTracker] a little rewrite as suggested

[Rares Visalom <raresvisalom src gnome org>]

commit 7b8da62767900e9c442124dda8470c3ed62923b5
Author: raresv <rares visalom gmail com>
Date:   Wed Jul 27 01:18:21 2016 +0300

    a little rewrite as suggested

 src/userTracker.js |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)
---
diff --git a/src/userTracker.js b/src/userTracker.js
index 85703be..3b21bb1 100644
--- a/src/userTracker.js
+++ b/src/userTracker.js
@@ -176,8 +176,7 @@ const UserTracker = new Lang.Class({
     _clearUsersFromRoom: function(room) {
         let map = this._getRoomContacts(room);
         for ([baseNick, contacts] of map)
-            while (contacts.length > 0)
-                this._untrackMember(contacts[0], room);
+            contacts.slice().forEach((m) => { this._untrackMember(m, room); });
     },
 
     _ensureRoomMappingForRoom: function(room) {