🐛 Fix chat summary failed when lastMessage is null

lib/models/chat.dart

@@ -104,7 +104,7 @@ sealed class SnChatMember with _$SnChatMember {
 sealed class SnChatSummary with _$SnChatSummary {
   const factory SnChatSummary({
     required int unreadCount,
-    required SnChatMessage lastMessage,
+    required SnChatMessage? lastMessage,
   }) = _SnChatSummary;
 
   factory SnChatSummary.fromJson(Map<String, dynamic> json) =>

lib/models/chat.g.dart

@@ -213,7 +213,10 @@ Map<String, dynamic> _$SnChatMemberToJson(_SnChatMember instance) =>
 _SnChatSummary _$SnChatSummaryFromJson(Map<String, dynamic> json) =>
     _SnChatSummary(
       unreadCount: (json['unread_count'] as num).toInt(),
-      lastMessage: SnChatMessage.fromJson(
+      lastMessage:
+          json['last_message'] == null
+              ? null
+              : SnChatMessage.fromJson(
                 json['last_message'] as Map<String, dynamic>,
               ),
     );
@@ -221,7 +224,7 @@ _SnChatSummary _$SnChatSummaryFromJson(Map<String, dynamic> json) =>
 Map<String, dynamic> _$SnChatSummaryToJson(_SnChatSummary instance) =>
     <String, dynamic>{
       'unread_count': instance.unreadCount,
-      'last_message': instance.lastMessage.toJson(),
+      'last_message': instance.lastMessage?.toJson(),
     };
 
 _MessageChange _$MessageChangeFromJson(Map<String, dynamic> json) =>

lib/screens/chat/chat.dart

@@ -79,18 +79,21 @@ class ChatRoomListTile extends HookConsumerWidget {
                     color: Theme.of(context).colorScheme.primary,
                   ),
                 ),
+              if (data.lastMessage == null)
+                Text(room.description ?? 'descriptionNone'.tr(), maxLines: 1)
+              else
                 Row(
                   spacing: 4,
                   children: [
                     Badge(
-                    label: Text(data.lastMessage.sender.account.nick),
+                      label: Text(data.lastMessage!.sender.account.nick),
                       textColor: Theme.of(context).colorScheme.onPrimary,
                       backgroundColor: Theme.of(context).colorScheme.primary,
                     ),
                     Expanded(
                       child: Text(
-                      (data.lastMessage.content?.isNotEmpty ?? false)
-                          ? data.lastMessage.content!
+                        (data.lastMessage!.content?.isNotEmpty ?? false)
+                            ? data.lastMessage!.content!
                             : 'messageNone'.tr(),
                         maxLines: 1,
                         overflow: TextOverflow.ellipsis,
@@ -100,7 +103,9 @@ class ChatRoomListTile extends HookConsumerWidget {
                     Align(
                       alignment: Alignment.centerRight,
                       child: Text(
-                      RelativeTime(context).format(data.lastMessage.createdAt),
+                        RelativeTime(
+                          context,
+                        ).format(data.lastMessage!.createdAt),
                         style: Theme.of(context).textTheme.bodySmall,
                       ),
                     ),