traceback when typing esc on a message windows

[misc]

If i open a chat windows with a contact, and close it using 'esc', i see a trace back in the console :

Traceback (most recent call last):
  File "/home/misc/checkout/svn/gajim/src/message_window.py", line 537, in _on_notebook_key_press
    self.remove_tab(ctrl, self.CLOSE_ESC)
  File "/home/misc/checkout/svn/gajim/src/message_window.py", line 322, in remove_tab
    self.show_title()
  File "/home/misc/checkout/svn/gajim/src/message_window.py", line 258, in show_title
    if control.type_id == message_control.TYPE_GC:
AttributeError: 'NoneType' object has no attribute 'type_id'

However, everything work fine.

[asterix]

(In [8131]) prevent TB when closing a window. fixes #3152

[asterix]

(In [8657]) prevent TB when closing a window. fixes #3152