Whe dose null check appears when I lose connection

FutureBuilder<List>( future: getCharacters(), builder: ( context, snapshot, ) { switch (snapshot.connectionState) { case ConnectionState.done: return ListView.builder( itemCount: charactersModel.data!.results!.length, itemBuilder: (context, index) => Column( children: [ Text( snapshot.data![index].name.toString(), ) ], ), );

                    case ConnectionState.waiting:
                      return Text('waiting');
                    default:
                      if (snapshot.hasError || snapshot.data == null) {
                        return const Center(
                          child: Text(
                              'Something went wrong, we are working on fixing it!'),
                        );
                      } else {
                        return Text('Nooooooooooone');
                      }
                  }
                }),