Fetches IPv4 and IPv6 information.
This function retrieves IPv4 and IPv6 address information using the `self.ip` interface.
If either IPv4 or IPv6 information is unavailable, it logs the event and returns an empty dictionary.
If both are available, the IPv6 address is added to the IPv4 info dictionary under the "ipv6" key.
Returns:
Dict[str, Any]: A dictionary containing IPv4 information, with the IPv6 address included if available.
Returns an empty dictionary if either IPv4 or IPv6 information is missing or if an error occurs.
Error Handling:
Logs any exceptions encountered during the fetching process and returns an empty dictionary.