ChannelListView NULL error when a channel has no messages

[funwithflutter]

When creating a new channel (for example, from the CLI), that does not have any messages in the channel, will cause ChannelListView widget to throw an error as there are no checks to see if the channel message list is empty.

The method 'toLocal' was called on null.
Receiver: null
Tried calling: toLocal()

The relevant error-causing widget was
    ChannelListView 
lib/main.dart:147
When the exception was thrown, this was the stack
#0      Object.noSuchMethod  (dart:core-patch/object_patch.dart:53:5)
#1      ChannelPreview._buildDate.<anonymous closure> 
package:stream_chat_flutter/src/channel_preview.dart:71
#2      StreamBuilder.build 
package:flutter/…/widgets/async.dart:425
#3      _StreamBuilderBaseState.build 
package:flutter/…/widgets/async.dart:125
#4      StatefulElement.build 
package:flutter/…/widgets/framework.dart:4334
... 

There needs to some validation to make sure there are messages, before calling:

final lastMessageAt = snapshot.data.toLocal(); in "channel_preview.dart"

Widget _buildDate(BuildContext context) {
    return StreamBuilder<DateTime>(
      stream: channel.lastMessageAtStream,
      initialData: channel.lastMessageAt,
      builder: (context, snapshot) {
        final lastMessageAt = snapshot.data.toLocal();

        String stringDate;
        final now = DateTime.now();

        if (now.year != lastMessageAt.year ||
            now.month != lastMessageAt.month ||
            now.day != lastMessageAt.day) {
          stringDate = Jiffy(lastMessageAt.toLocal()).format('dd/MM/yyyy');
        } else {
          stringDate = Jiffy(lastMessageAt.toLocal()).format('HH:mm');
        }

        return Text(
          stringDate,
          style: StreamChatTheme.of(context).channelPreviewTheme.lastMessageAt,
        );
      },
    );
  }