Preserve the offset invariant.

samples/memfs/inode.go

@@ -192,6 +192,7 @@ func (inode *inode) RemoveChild(name string) {
 	// Mark it as unused.
 	inode.entries[i] = fuseutil.Dirent{
 		Type:   fuseutil.DT_Unknown,
+		Offset: fuse.DirOffset(i + 1),
 	}
 }