Remove redundant functions

lib/download_handler.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 
+import 'package:collection/collection.dart';
 import 'package:flutter/material.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/account.dart';
@@ -7,7 +8,6 @@ import 'package:nc_photos/app_localizations.dart';
 import 'package:nc_photos/entity/file.dart';
 import 'package:nc_photos/exception.dart';
 import 'package:nc_photos/exception_util.dart' as exception_util;
-import 'package:nc_photos/iterable_extension.dart';
 import 'package:nc_photos/k.dart' as k;
 import 'package:nc_photos/mobile/android/download.dart';
 import 'package:nc_photos/mobile/notification.dart';

lib/entity/album/upgrader.dart

@@ -1,9 +1,9 @@
+import 'package:collection/collection.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/account.dart';
 import 'package:nc_photos/ci_string.dart';
 import 'package:nc_photos/entity/exif.dart';
 import 'package:nc_photos/entity/file.dart';
-import 'package:nc_photos/iterable_extension.dart';
 import 'package:nc_photos/type.dart';
 import 'package:tuple/tuple.dart';
 

lib/iterable_extension.dart

@@ -56,20 +56,4 @@ extension IterableExtension<T> on Iterable<T> {
     return where((element) =>
         s.add(OverrideComparator<T>(element, equalFn, hashCodeFn))).toList();
   }
-
-  T? get firstOrNull {
-    try {
-      return first;
-    } on StateError catch (_) {
-      return null;
-    }
-  }
-
-  T? get lastOrNull {
-    try {
-      return last;
-    } on StateError catch (_) {
-      return null;
-    }
-  }
 }

pubspec.lock

@@ -107,7 +107,7 @@ packages:
     source: hosted
     version: "1.1.0"
   collection:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: collection
       url: "https://pub.dartlang.org"

pubspec.yaml

@@ -30,6 +30,7 @@ dependencies:
   android_intent_plus: ^3.0.1
   bloc: ^7.0.0
   cached_network_image: ^3.0.0
+  collection: ^1.15.0
   connectivity_plus: ^2.0.2
   device_info_plus: ^3.1.0
   draggable_scrollbar:

test/test_util.dart

@@ -1,3 +1,4 @@
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:idb_shim/idb.dart';
 import 'package:logging/logging.dart';