unmount error with dkvolume

[Mulefire]

This is a great plugin, I hope you continue with it!

I receive the following error when unmounting a share and running with commit ca66de9.

I did not receive this error on commit 978fbe9.

The plugin is running on an Ubuntu 15.04 host with Docker 1.8.0-dev Rev 8c7cd78.

Steps to reproduce:

1. cd docker-volume-nfs
2. make build
3. ./app
4. docker run --rm --name nfs-test --volume-driver=nfs -v <share_ip>/<share_path>:/tmp/mnt busybox ls -la /tmp/mnt

Let me know if I can provide more information,

Thanks!

2015/07/17 10:31:18 http: panic serving @: runtime error: invalid memory address or nil pointer dereference
goroutine 12 [running]:
net/http.(_conn).serve.func1(0xc8200b09a0, 0x7f02453ed798, 0xc82002e0c8)
/usr/local/go/src/net/http/server.go:1220 +0xb5
main.nfsDriver.Unmount(0xc820010600, 0x1c, 0xc8200e2e60, 0x1e, 0x0, 0x0, 0x0, 0x0)
/go/src/app/main.go:76 +0x32d
main.(_nfsDriver).Unmount(0xc82000aba0, 0xc8200e2e60, 0x1e, 0x0, 0x0, 0x0, 0x0)
:5 +0xc2
app/vendor/github.com/calavera/docker-volume-api.(_Handler).initMux.func6(0xc8200e2e60, 0x1e, 0x0, 0x0, 0x0, 0x0)
/go/src/app/vendor/github.com/calavera/docker-volume-api/api.go:87 +0x66
app/vendor/github.com/calavera/docker-volume-api.(_Handler).handle.func1(0x7f02453ed940, 0xc8200e69a0, 0xc8200f2c40)
/go/src/app/vendor/github.com/calavera/docker-volume-api/api.go:98 +0x97
net/http.HandlerFunc.ServeHTTP(0xc82000ac40, 0x7f02453ed940, 0xc8200e69a0, 0xc8200f2c40)
/usr/local/go/src/net/http/server.go:1355 +0x3a
net/http.(_ServeMux).ServeHTTP(0xc820012c60, 0x7f02453ed940, 0xc8200e69a0, 0xc8200f2c40)
/usr/local/go/src/net/http/server.go:1632 +0x17d
net/http.serverHandler.ServeHTTP(0xc820018180, 0x7f02453ed940, 0xc8200e69a0, 0xc8200f2c40)
/usr/local/go/src/net/http/server.go:1795 +0x19e
net/http.(_conn).serve(0xc8200b09a0)
/usr/local/go/src/net/http/server.go:1294 +0xbea
created by net/http.(*Server).Serve
/usr/local/go/src/net/http/server.go:1843 +0x3f6