progress shouldn't be required

Author: contactjavas

flutter_cache_manager/example/lib/plugin_example/progress_indicator.dart

@@ -8,7 +8,7 @@ class ProgressIndicator extends StatelessWidget {
 
   const ProgressIndicator({
     Key? key,
-    required this.progress,
+    this.progress,
   }) : super(key: key);
 
   @override
@@ -21,7 +21,9 @@ class ProgressIndicator extends StatelessWidget {
             width: 50.0,
             height: 50.0,
             child: CircularProgressIndicator(
-              value: progress.progress,
+              value: progress != null && progress?.progress != null
+                  ? progress?.progress
+                  : null,
             ),
           ),
           const SizedBox(width: 20),

flutter_cache_manager/lib/src/cache_manager.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:typed_data';
 
 import 'package:file/file.dart';
 import 'package:flutter/foundation.dart' show visibleForTesting;