Fix view_ids for board when empty

(transplanted from 508f94b426b1f816cabceb6c3f333d992afb1794)

tryton/gui/window/window.py

@@ -31,8 +31,8 @@ class Window(object):
             Main.get_main().win_add(win)
         elif view_type == 'board':
             from board import Board
-            win = Board(window, view_ids[0], context=context, name=name,
-                    auto_refresh=auto_refresh)
+            win = Board(window, view_ids and view_ids[0] or None,
+                    context=context, name=name, auto_refresh=auto_refresh)
             Main.get_main().win_add(win)
         else:
             import logging