fix bug in qd
fix bug in qd

cr-marcstevens/fplll,shi-bai/fplll,cr-marcstevens/fplll,dstehle/fplll,shi-bai/fplll,shi-bai/fplll,dstehle/fplll,shi-bai/fplll,blowfish880/fplll,fplll/fplll,blowfish880/fplll,cr-marcstevens/fplll,fplll/fplll,fplll/fplll,fplll/fplll,cr-marcstevens/fplll,fplll/fplll,dstehle/fplll,blowfish880/fplll