Use the right way to copy a list in python, thanks Yann.

src/roster_window.py

@@ -852,7 +852,6 @@ class RosterWindow:
 			item.connect('activate', self.on_bookmark_menuitem_activate,
 				account, bookmark)
 			gc_sub_menu.append(item)
-	
 
 	def _change_style(self, model, path, iter, option):
 		if option is None:

src/systray.py

@@ -271,7 +271,9 @@ class Systray:
 		# if we sort_by_show : contacts_table = [group, status, name]
 		# else : contacts_table = [group,  name, status]
 		contacts_table = []
-		show_list = gajim.SHOW_LIST
+		show_list = []
+		for show in gajim.SHOW_LIST: # copy gajim.SHOW_LIST in show_list
+	   		show_list.append(show)
 		show_list.append('not in roster') # not in roster is not in this list but we need it
 		for jid in gajim.contacts.get_jid_list(account):
 			contact = gajim.contacts.get_contact_with_highest_priority(account,