@ makes more sense since the NUL addr contained in the sockaddr's
sun_path field can also be written as ^@.
Also, in the .socket files writing "ListenStream==foo" is kinda ugly.
Finally, tools like strace decode it with an @ too.
if we ask for more than one from the kernel we might need to check for
the validity of the ptr element since event might be processed after its
ptr was already destructed.