Fix: Handle getLastMessage when no message exists

lib/components/user_tile_chats.dart

@@ -72,12 +72,14 @@ class UserTileChats extends StatelessWidget {
         if (snapshot.connectionState == ConnectionState.waiting) {
           return const CircularProgressIndicator();
         } else if (snapshot.hasError) {
-          return Text(
-            'Error: ${snapshot.error}',
+          return Expanded(
+            child: Text(
+              'Error <last message>: ${snapshot.error}',
               style: const TextStyle(color: Colors.red),
+            ),
           );
         } else if (!snapshot.hasData || snapshot.data == null) {
-          return const Text('No messages yet');
+          return buildMsgDetails('No messages yet', '', null);
         } else {
           Message lastMessage = snapshot.data!;
           msgDateString = formatTimestamp(lastMessage.timestamp);
@@ -90,6 +92,14 @@ class UserTileChats extends StatelessWidget {
             outgoing = false;
           }
 
+          return buildMsgDetails(msgContent, msgDateString, outgoing);
+        }
+      },
+    );
+  }
+
+  Widget buildMsgDetails(
+      String msgContent, String msgDateString, bool? outgoing) {
     return Expanded(
       child: Column(
         crossAxisAlignment: CrossAxisAlignment.start,
@@ -133,7 +143,4 @@ class UserTileChats extends StatelessWidget {
       ),
     );
   }
-      },
-    );
-  }
 }

lib/services/chat/chat_service.dart

@@ -1,5 +1,6 @@
 import 'package:cloud_firestore/cloud_firestore.dart';
 import 'package:firebase_auth/firebase_auth.dart';
+import 'package:flutter/foundation.dart' show debugPrint;
 
 import '../../constants.dart';
 import '../../utils/helper.dart';
@@ -58,13 +59,16 @@ class ChatService {
   }
 
   /// Retrieves the last message of a chatroom.
-  Future<Message> getLastMessage(String chatRoomID) async {
+  ///
+  /// Returns [null] in case of an error.
+  Future<Message?> getLastMessage(String chatRoomID) async {
     String senderID = '';
     String senderEmail = '';
     String receiverID = '';
     String message = '';
-    Timestamp timestamp = Timestamp.fromDate(DateTime.utc(1970, 01, 01));
+    Timestamp timestamp = Timestamp.fromMillisecondsSinceEpoch(0);
 
+    try {
       QuerySnapshot messageSnapshot = await _firestore
           .collection(Constants.dbCollectionChatRooms)
           .doc(chatRoomID)
@@ -81,6 +85,10 @@ class ChatService {
         message = lastMessageDoc[Constants.dbFieldMessageText];
         timestamp = lastMessageDoc[Constants.dbFieldMessageTimestamp];
       }
+    } catch (e) {
+      debugPrint(e.toString());
+      return null;
+    }
 
     return Message(
       senderID: senderID,