Sets the navigation model for this edit.
        
        :param      model | <XNavigationModel>

def setNavigationModel( self, model ):
        """
        Sets the navigation model for this edit.
        
        :param      model | <XNavigationModel>
        """
        self._navigationModel = model
        self._completerTree.setModel(model)
        
        if ( model ):
            model.setSeparator(self.separator())
            completer = XNavigationCompleter(model, self)
            self.setCompleter(completer)
            completer.popup().installEventFilter(self)
        else:
            self.setCompleter(None)
        
        self.rebuild()