fix bug when cuda not installed and cuda.fuse decorator used without parenthesis
fix bug when cuda not installed and cuda.fuse decorator used without parenthesis

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