Can you give one example where this entry could exist without internet connection?
I. e. you apparently consider that the network without the Internet does not exist?
The network with the router has a separate entry. If you control the settings of your router using 192.168.44.1, for instance, you'll have an entry in the routing table with network destination value of 192.168.44.0.
If your computer is part of a local network that holds 60 computers with IP numbers from 192.168.0.2-->61, you will have an entry with 192.168.0.0.
When your system discovers that your computer can reach 8.8.8.8 through your router on 192.168.44.1, it adds the 0.0.0.0 entry for you. It will delete this entry when it fails, or when 192.168.44.1 disconnects (hardware) or disappears (Software: ARP packets receive no response).