wxGUI iclass: fix indentation

git-svn-id: https://svn.osgeo.org/grass/grass/branches/releasebranch_7_0@64323 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/iclass/frame.py

@@ -86,6 +86,7 @@ class IClassMapFrame(DoubleMapFrame):
                                 firstMap = Map(), secondMap = Map(),
                                 **kwargs)
         self._giface = giface
+        self.tree = None
         self.mapWindowProperties = MapWindowProperties()
         self.mapWindowProperties.setValuesFromUserSettings()
         # show computation region by defaut