fix std::string{} to std::string() not to interpreted as initializer_list
fix std::string{} to std::string() not to interpreted as initializer_list

chainer/chainer,hvy/chainer,ktnyt/chainer,wkentaro/chainer,pfnet/chainer,wkentaro/chainer,hvy/chainer,hvy/chainer,chainer/chainer,ktnyt/chainer,chainer/chainer,wkentaro/chainer,niboshi/chainer,niboshi/chainer,keisuke-umezawa/chainer,okuta/chainer,jnishi/chainer,wkentaro/chainer,chainer/chainer,jnishi/chainer,keisuke-umezawa/chainer,okuta/chainer,hvy/chainer,niboshi/chainer,ktnyt/chainer,okuta/chainer,tkerola/chainer,niboshi/chainer,jnishi/chainer,keisuke-umezawa/chainer,okuta/chainer,ktnyt/chainer,keisuke-umezawa/chainer,jnishi/chainer