fix wrong Row number in DiscoveryDialog.py that caused following traceback:

Traceback (most recent call last):
File "/home/beremiz/beremiz/ProjectController.py", line 1536, in _Connect
dialog = DiscoveryDialog(self.AppFrame)
File "/home/beremiz/beremiz/dialogs/DiscoveryDialog.py", line 124, in __init__
self._init_ctrls(parent)
File "/home/beremiz/beremiz/dialogs/DiscoveryDialog.py", line 121, in _init_ctrls
self._init_sizers()
File "/home/beremiz/beremiz/dialogs/DiscoveryDialog.py", line 73, in _init_sizers
self._init_coll_ButtonGridSizer_Growables(self.ButtonGridSizer)
File "/home/beremiz/beremiz/dialogs/DiscoveryDialog.py", line 64, in _init_coll_ButtonGridSizer_Growables
parent.AddGrowableRow(1)
File "/usr/lib/python2.7/dist-packages/wx-3.0-gtk2/wx/_core.py", line 15343, in AddGrowableRow
return _core_.FlexGridSizer_AddGrowableRow(*args, **kwargs)
PyAssertionError: C++ assertion "!m_rows || idx < (size_t)m_rows" failed at ../src/common/sizer.cpp(1967) in AddGrowableRow(): invalid row index

libraries = [
    ('Native', 'NativeLib.NativeLibrary'),
    ('Python', 'py_ext.PythonLibrary'),
    ('SVGUI', 'svgui.SVGUILibrary')]

catalog = [
    ('canfestival', _('CANopen support'), _('Map located variables over CANopen'), 'canfestival.canfestival.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 = []