Load images for EtherCAT extension

Fixes following backtrace:

Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/wx-3.0-gtk3/wx/_core.py", line 16765, in <lambda>
lambda event: event.callable(*event.args, **event.kw) )
File "/home/developer/WorkData/PLC/beremiz/beremiz/BeremizIDE.py", line 1074, in AddConfNode
self._Refresh(TITLE, FILEMENU, PROJECTTREE)
File "/home/developer/WorkData/PLC/beremiz/beremiz/IDEFrame.py", line 917, in _Refresh
self.RefreshFunctions[element]()
File "/home/developer/WorkData/PLC/beremiz/beremiz/IDEFrame.py", line 1526, in RefreshProjectTree
self.GenerateProjectTreeBranch(root, infos)
File "/home/developer/WorkData/PLC/beremiz/beremiz/IDEFrame.py", line 1565, in GenerateProjectTreeBranch
self.GenerateProjectTreeBranch(item, values)
File "/home/developer/WorkData/PLC/beremiz/beremiz/IDEFrame.py", line 1554, in GenerateProjectTreeBranch
self.TreeImageDict[icon_name] = self.TreeImageList.Add(GetBitmap(icon_name))
File "/usr/lib/python2.7/dist-packages/wx-3.0-gtk3/wx/_gdi.py", line 6735, in Add
return _gdi_.ImageList_Add(*args, **kwargs)
ValueError: invalid null reference in method 'ImageList_Add', expected argument 2 of type 'wxBitmap const &

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                  <xsd:element name="Xenomai">

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                    <xsd:complexType>

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                      %(toolchain_gcc)s

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                      <xsd:attribute name="XenoConfig" type="xsd:string" use="optional" default="xeno-config"/>

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                    </xsd:complexType>

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                  </xsd:element>