NFS: Fix a potential NULL dereference in nfs_get_client()

None of the callers are expecting NULL returns from nfs_get_client() so
this code will lead to an Oops. It's better to return an error
pointer. I expect that this is dead code so hopefully no one is
affected.

Fixes: 31434f496abb ("nfs: check hostname in nfs_get_client")
Signed-off-by: Dan Carpenter <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/client.c

···
 
 	if (cl_init->hostname == NULL) {
 		WARN_ON(1);
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	/* see if the client already exists */