Fix "Show extensions" Button

The "Show extensions" Button was not working properly when categories were hidden.
An Exception would throw:
```
_AssertionError ('package:flutter/src/material/tab_controller.dart': Failed assertion: line 202 pos 12: 'value >= 0 && (value < length || length == 0)': is not true.)
```
And jump to the end of the tab list regardless of where you clicked the button.

lib/modules/browse/browse_screen.dart

@@ -197,6 +197,7 @@ class _BrowseScreenState extends ConsumerState<BrowseScreen>
             if (tab.kind == BrowseTabKind.sources) {
               return SourcesScreen(
                 itemType: tab.type,
+                tabs: _tabList,
                 tabIndex: (index) => _tabBarController.animateTo(index),
               );
             } else {

lib/modules/browse/sources/sources_screen.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:mangayomi/modules/browse/browse_screen.dart';
 import 'package:mangayomi/modules/widgets/custom_sliver_grouped_list_view.dart';
 import 'package:isar_community/isar.dart';
 import 'package:mangayomi/main.dart';
@@ -11,10 +12,12 @@ import 'package:mangayomi/utils/language.dart';
 
 class SourcesScreen extends ConsumerStatefulWidget {
   final Function(int) tabIndex;
+  final List<BrowseTab> tabs;
   final ItemType itemType;
   const SourcesScreen({
     required this.tabIndex,
     required this.itemType,
+    required this.tabs,
     super.key,
   });
 
@@ -62,13 +65,17 @@ class _SourcesScreenState extends ConsumerState<SourcesScreen> {
                 Padding(
                   padding: const EdgeInsets.all(8.0),
                   child: ElevatedButton.icon(
-                    onPressed: () => widget.tabIndex(
-                      widget.itemType == ItemType.manga
-                          ? 3
-                          : widget.itemType == ItemType.anime
-                          ? 4
-                          : 5,
-                    ),
+                    onPressed: () {
+                      final extensionIndex = widget.tabs.indexWhere(
+                        (t) =>
+                            t.type == widget.itemType &&
+                            t.kind == BrowseTabKind.extensions,
+                      );
+
+                      if (extensionIndex != -1) {
+                        widget.tabIndex(extensionIndex);
+                      }
+                    },
                     icon: const Icon(Icons.extension_rounded),
                     label: Text(context.l10n.show_extensions),
                   ),