I watched the Tutorial from Google about Firestore, but i came up with problems about “null exception”. I imported the package and all, but i dont get the answer.

Main Page

StreamBuilder(
          stream: FirebaseFirestore.instance.collection("testCity").snapshots(),
          builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.waiting) {
              return const Text("Bitte Warten");
            }

            return ListView.separated(

              padding: const EdgeInsets.fromLTRB(24, 16, 24, 24),
              physics: const NeverScrollableScrollPhysics(),
              shrinkWrap: true,

              itemCount: snapshot.data.docs.length,
              itemBuilder: (context, int index) {
                return NormalCard(database: snapshot.data.docs[index]);
              },

              separatorBuilder: (BuildContext context, int index)
              => const Divider(
                height: 32,
                thickness: 4,
                color: Color(0xFF484848),
              ),
            );
          },
        )

Normalcard Widget

class NormalCard extends StatefulWidget {
  const NormalCard({Key? key, required this.database}) : super(key: key);

  final DocumentSnapshot database;

  @override
  State<NormalCard> createState() => _NormalCardState();
}

class _NormalCardState extends State<NormalCard> {

  @override
  Widget build(BuildContext context) {

    DocumentSnapshot database = widget.database;

    return LayoutBuilder(
      ...
    );
  }
}

Following Errors occured:
at Problems Tab:
“The property ‘docs’ can’t be unconditionally accessed because the receiver can be ‘null’.”

at run:
lib/Pages/page_startseite.dart:80:40: Error: Property ‘docs’ cannot be accessed on ‘QuerySnapshot<Map<String, dynamic>>?’ because it is potentially null.

• ‘QuerySnapshot’ is from ‘package:cloud_firestore/cloud_firestore.dart’ (‘../../../AppData/Local/Pub/Cache/hosted/pub.dev/cloud_firestore-4.14.0/lib/cloud_firestore.dart’).
• ‘Map’ is from ‘dart:core’.
  Try accessing using ?. instead.
  itemCount: snapshot.data.docs.length,
  ^^^^
  lib/Pages/page_startseite.dart:82:59: Error: Property ‘docs’ cannot be accessed on ‘QuerySnapshot<Map<String, dynamic>>?’ because it is potentially null.
• ‘QuerySnapshot’ is from ‘package:cloud_firestore/cloud_firestore.dart’ (‘../../../AppData/Local/Pub/Cache/hosted/pub.dev/cloud_firestore-4.14.0/lib/cloud_firestore.dart’).
• ‘Map’ is from ‘dart:core’.
  Try accessing using ?. instead.
  return NormalCard(database: snapshot.data.docs[index]);
  ^^^^
  lib/Pages/page_exploreseite.dart:112:40: Error: Required named parameter ‘database’ must be provided.
  return const NormalCard();
  ^
  lib/Widgets/card_restaurantNormal.dart:5:9: Context: Found this candidate, but the arguments don’t match.
  const NormalCard({Key? key, required this.database}) : super(key: key);
  ^^^^^^^^^^

Can anyone help me with this problems so i can implement my Database from Firestore as Backend of my Project?