fix bug that appears if datatype in the project tree is renamed to wrong name (keyword, existend type,...)

Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/wx-3.0-gtk2/wx/_core.py", line 16765, in <lambda>
lambda event: event.callable(*event.args, **event.kw) )
File "/usr/lib/python2.7/dist-packages/wx-3.0-gtk2/wx/lib/expando.py", line 126, in _adjustCtrl
numLines = self.GetNumberOfLines()
File "/usr/lib/python2.7/dist-packages/wx-3.0-gtk2/wx/_core.py", line 16710, in __getattr__
raise PyDeadObjectError(self.attrStr % self._name)
PyDeadObjectError: The C++ part of the TreeTextCtrl object has been deleted, attribute access no longer allowed.

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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>