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

<?xml version='1.0' encoding='utf-8'?>
<PyFile xmlns:xhtml="http://www.w3.org/1999/xhtml" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <variables/>
  <globals>
    <xhtml:p><![CDATA[]]></xhtml:p>
  </globals>
  <init>
    <xhtml:p><![CDATA[]]></xhtml:p>
  </init>
  <cleanup>
    <xhtml:p><![CDATA[]]></xhtml:p>
  </cleanup>
  <start>
    <xhtml:p><![CDATA[]]></xhtml:p>
  </start>
  <stop>
    <xhtml:p><![CDATA[]]></xhtml:p>
  </stop>
</PyFile>