fix weighted mode of MassScalarTerm
fix weighted mode of MassScalarTerm

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