feat: Fix framework assertion when adding an item

lib/main.dart

@@ -122,9 +122,13 @@ class MyApp extends StatelessWidget {
         if (state is NoopNavigationState) {
           // NOOP
         } else if (state is PushNavigationState) {
-          _router.go(state.destination);
-        } else if (state is GoNavigationState) {
           _router.push(state.destination);
+        } else if (state is GoNavigationState) {
+          if (_router.canPop()) {
+            _router.replace(state.destination);
+          } else {
+            _router.go(state.destination);
+          }
         } else if (state is PoppedNavigationState) {
           _router.pop();
         }

lib/src/ui/widgets/image.dart

@@ -4,7 +4,7 @@ import 'package:flutter/material.dart';
 class AnimeCoverImage extends StatelessWidget {
   const AnimeCoverImage({
     required this.url,
-    required this.hero,
+    this.hero,
     this.cached = true,
     this.extra,
     this.onTap,
@@ -18,7 +18,7 @@ class AnimeCoverImage extends StatelessWidget {
   final bool cached;
 
   /// The hero tag of the image.
-  final String hero;
+  final String? hero;
 
   /// An extra widget with a translucent backdrop.
   final Widget? extra;
@@ -28,9 +28,7 @@ class AnimeCoverImage extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return Hero(
-      tag: hero,
-      child: ClipRRect(
+    final image = ClipRRect(
       borderRadius: BorderRadius.circular(8),
       child: Material(
         child: SizedBox(
@@ -74,7 +72,15 @@ class AnimeCoverImage extends StatelessWidget {
           ),
         ),
       ),
-      ),
+    );
+
+    if (hero != null) {
+      return Hero(
+        tag: hero!,
+        child: image,
       );
     }
+
+    return image;
+  }
 }

lib/src/ui/widgets/list_item.dart

@@ -76,8 +76,6 @@ class ListItem extends StatelessWidget {
           children: [
             AnimeCoverImage(
               cached: cached,
-              // TODO(Unknown): Have the ID here
-              hero: thumbnailUrl,
               extra: imageExtra,
               url: thumbnailUrl,
             ),