std.os.accept already wants to allow null, which matches `man 3p accept`:
> address Either a null pointer, or a pointer to a sockaddr structure
> where the address of the connecting socket shall be re‐
> turned.
>
> address_len Either a null pointer, if address is a null pointer, or a
> pointer to a socklen_t object which on input specifies the
> length of the supplied sockaddr structure, and on output
> specifies the length of the stored address.
Fixes ziglang#6832.
23c28c72b7