Fix wxHMI example after upgrading wxGlade

Newer wxGlade generates code to initialize GridSizer's with empty
elements.

...
grid_sizer_1.Add(self.window_1, 1, wx.ALIGN_CENTER, 0)
sizer_2.Add((0, 0), 0, 0, 0)
sizer_2.Add((0, 0), 0, 0, 0)
sizer_2.Add((0, 0), 0, 0, 0)
sizer_2.Add((0, 0), 0, 0, 0)
...

That causes following traceback, if new buttons are added
to already full sizer.

PLCobject : Traceback (most recent call last):

File "./Beremiz_service.py", line 389, in default_evaluator
res = (tocall(*args, **kwargs), None)

File "/tmp/tmpQS8ct2/runtime_0.py", line 540, in _runtime_0_start
wx.MessageBox(_("Please stop PLC to close"))

File "/tmp/tmpQS8ct2/runtime_0.py", line 504, in Init
lambda axis:( MakeButtonFunc(self, sizer, axis+"axisMinus"),

File "/tmp/tmpQS8ct2/runtime_0.py", line 502, in <lambda>
lambda btname: MakeButtonFunc(self, sizer, btname), ActionButtons)

File "/tmp/tmpQS8ct2/runtime_0.py", line 461, in MakeButtonFunc
print sizer, btname

File "/usr/lib/python2.7/dist-packages/wx-3.0-gtk3/wx/_core.py", line 14453, in Add
return _core_.Sizer_Add(*args, **kwargs)

PyAssertionError: C++ assertion "Assert failure" failed at
../src/common/sizer.cpp(1401) in DoInsert(): too many items (11 > 2*5)
in grid sizer (maybe you should omit the number of either rows or
columns?)


Tested with wxGlade version 0.8.3
Closes #41

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# This file is part of Beremiz
#
# Copyright (C) 2007: Laurent BESSARD
# Copyright (C) 2007-2018: Edouard TISSERANT
#
# See COPYING file for copyrights details.

libraries = [
    ('Native', 'NativeLib.NativeLibrary', True),
    ('Python', 'py_ext.PythonLibrary', True),
    ('Etherlab', 'etherlab.EthercatMaster.EtherlabLibrary', False),
    ('SVGUI', 'svgui.SVGUILibrary', False)]

catalog = [
    ('canfestival', _('CANopen support'), _('Map located variables over CANopen'), 'canfestival.canfestival.RootClass'),
    ('bacnet', _('Bacnet support'), _('Map located variables over Bacnet'), 'bacnet.bacnet.RootClass'),
    ('etherlab', _('EtherCAT master'), _('Map located variables over EtherCAT'), 'etherlab.etherlab.RootClass'),
    ('modbus', _('Modbus support'), _('Map located variables over Modbus'), 'modbus.modbus.RootClass'),
    ('c_ext', _('C extension'), _('Add C code accessing located variables synchronously'), 'c_ext.CFile'),
    ('py_ext', _('Python file'), _('Add Python code executed asynchronously'), 'py_ext.PythonFile'),
    ('wxglade_hmi', _('WxGlade GUI'), _('Add a simple WxGlade based GUI.'), 'wxglade_hmi.WxGladeHMI'),
    ('svgui', _('SVGUI'), _('Experimental web based HMI'), 'svgui.SVGUI')]

file_editors = []