fix for last message sent on analytics list tiles

lib/pangea/models/analytics/chart_analytics_model.dart

@@ -137,4 +137,13 @@ class ChartAnalyticsModel {
     }
     timeSeries = intervals.values.toList().reversed.toList();
   }
+
+  DateTime? get lastMessageTime {
+    if (msgs.isEmpty) {
+      return null;
+    }
+    return msgs.map((msg) => msg.time).reduce(
+          (compare, recent) => compare.isAfter(recent) ? compare : recent,
+        );
+  }
 }

lib/pangea/pages/analytics/analytics_list_tile.dart

@@ -122,7 +122,7 @@ class AnalyticsListTileState extends State<AnalyticsListTile> {
               Tooltip(
                 message: L10n.of(context)!.timeOfLastMessage,
                 child: Text(
-                  tileData?.lastMessage?.localizedTimeShort(context) ?? "",
+                  tileData?.lastMessageTime?.localizedTimeShort(context) ?? "",
                   style: TextStyle(
                     fontSize: 13,
                     color: Theme.of(context).textTheme.bodyMedium!.color,