Get information about users & groups related to the notifications

lib/helpers/groups_helper.dart

@@ -54,6 +54,17 @@ class GroupsHelper {
     return list;
   }
 
+  /// Get a list of groups from the server. In case of error, this method throws
+  /// an exception
+  Future<GroupsList> getListOrThrow(Set<int> groups,
+      {bool force = false}) async {
+    final list = await getList(groups, force: force);
+
+    if (list == null) throw Exception("Could not get the list of groups!");
+
+    return list;
+  }
+
   /// Get a list of groups from the server
   Future<GroupsList> getList(Set<int> groups, {bool force = false}) async {
     final list = GroupsList();