null safety

lib/pages/widgets/show_multiple_img.dart

@@ -8,14 +8,14 @@ class ShowMultiImage extends StatefulWidget {
   final List<DisplayImageSource> displayImageSources;
   final int initialPage;
   const ShowMultiImage(
-      {Key key, this.displayImageSources, this.initialPage = 0})
+      {Key? key, required this.displayImageSources, this.initialPage = 0})
       : super(key: key);
   @override
   _ShowMultiImageState createState() => _ShowMultiImageState();
 }
 
 class _ShowMultiImageState extends State<ShowMultiImage> {
-  PageController pageController;
+  late PageController pageController;
   @override
   void initState() {
     pageController = PageController(initialPage: widget.initialPage);
@@ -58,7 +58,7 @@ class _ShowMultiImageState extends State<ShowMultiImage> {
                       value: event == null
                           ? 0
                           : event.cumulativeBytesLoaded /
-                              event.expectedTotalBytes,
+                              event.expectedTotalBytes!,
                     ),
                   ),
                 ),