Error when opening multiple chat windows with differenct ressources for the same contact

Bug description

Traceback (most recent call last): File "/usr/share/gajim/src/message_window.py", line 824, in _on_notebook_switch_page new_ctrl.set_control_active(True) AttributeError: 'NoneType' object has no attribute 'set_control_active'

Steps to reproduce

Software versions

OS version:

arch linux

GTK version:

gtk2 2.24.31-1

gtk3 3.22.26+47+g3a1a7135a2-3

PyGTK version:

pygtk 2.24.0-8

Gajim 0.16.9-1