Textual value for boolean must be boolean

tryton/gui/window/view_form/view/list_gtk/parser.py

@@ -251,7 +251,7 @@ class Boolean(Int):
         self.renderer.connect('toggled', self._sig_toggled)
 
     def get_textual_value(self, model):
-        return model[self.field_name].get_client(model) or 0
+        return model[self.field_name].get_client(model)
 
     def setter(self, column, cell, store, iter):
         model = store.get_value(iter, 0)