fix errors in sequence_slice_op
fix errors in sequence_slice_op

PaddlePaddle/Paddle,Canpio/Paddle,PaddlePaddle/Paddle,baidu/Paddle,putcn/Paddle,pkuyym/Paddle,putcn/Paddle,QiJune/Paddle,Canpio/Paddle,jacquesqiao/Paddle,reyoung/Paddle,Canpio/Paddle,chengduoZH/Paddle,jacquesqiao/Paddle,QiJune/Paddle,jacquesqiao/Paddle,reyoung/Paddle,luotao1/Paddle,baidu/Paddle,tensor-tang/Paddle,luotao1/Paddle,PaddlePaddle/Paddle,pkuyym/Paddle,reyoung/Paddle,PaddlePaddle/Paddle,pkuyym/Paddle,chengduoZH/Paddle,chengduoZH/Paddle,putcn/Paddle,pkuyym/Paddle,PaddlePaddle/Paddle,jacquesqiao/Paddle,QiJune/Paddle,Canpio/Paddle,QiJune/Paddle,QiJune/Paddle,putcn/Paddle,jacquesqiao/Paddle,Canpio/Paddle,baidu/Paddle,Canpio/Paddle,Canpio/Paddle,reyoung/Paddle,putcn/Paddle,luotao1/Paddle,Canpio/Paddle,putcn/Paddle,luotao1/Paddle,luotao1/Paddle,QiJune/Paddle,pkuyym/Paddle,pkuyym/Paddle,baidu/Paddle,tensor-tang/Paddle,reyoung/Paddle,PaddlePaddle/Paddle,tensor-tang/Paddle,luotao1/Paddle,tensor-tang/Paddle,tensor-tang/Paddle,PaddlePaddle/Paddle,chengduoZH/Paddle,baidu/Paddle,chengduoZH/Paddle,jacquesqiao/Paddle,luotao1/Paddle,reyoung/Paddle