remove unused attribute of CharacteristicFunction
remove unused attribute of CharacteristicFunction

lokik/sfepy,BubuLK/sfepy,sfepy/sfepy,rc/sfepy,RexFuzzle/sfepy,RexFuzzle/sfepy,sfepy/sfepy,vlukes/sfepy,rc/sfepy,lokik/sfepy,RexFuzzle/sfepy,vlukes/sfepy,sfepy/sfepy,BubuLK/sfepy,lokik/sfepy,vlukes/sfepy,rc/sfepy,BubuLK/sfepy,lokik/sfepy,RexFuzzle/sfepy