Use better way to handle gallery with no images and page with no images

lib/components/gallery_basic_info.dart

@@ -10,7 +10,7 @@ class GalleryBasicInfo extends StatelessWidget {
   const GalleryBasicInfo(this.gMeta, this.firstPage,
       {super.key, this.fileId, this.gData, this.files});
   final GMeta gMeta;
-  final ExtendedPMeta firstPage;
+  final ExtendedPMeta? firstPage;
   final int? fileId;
   final GalleryData? gData;
   final EhFiles? files;
@@ -27,7 +27,9 @@ class GalleryBasicInfo extends StatelessWidget {
                 flex: 2,
                 child: Container(
                   margin: const EdgeInsets.only(right: 8),
-                  child: Thumbnail(firstPage, fileId: fileId, gid: gMeta.gid),
+                  child: firstPage != null
+                      ? Thumbnail(firstPage!, fileId: fileId, gid: gMeta.gid)
+                      : Container(),
                 )),
             Expanded(
                 flex: 3,

lib/components/gallery_info.dart

@@ -53,9 +53,9 @@ class _GalleryInfo extends State<GalleryInfo> with ThemeModeWidget {
   @override
   Widget build(BuildContext context) {
     bool useMobile = MediaQuery.of(context).size.width <= 810;
-    final firstPage = widget.gData.pages.first;
-    final int? firstFileId = widget.files != null
-        ? widget.files!.files[firstPage.token]!.first.id
+    final firstPage = widget.gData.pages.firstOrNull;
+    final int? firstFileId = widget.files != null && firstPage != null
+        ? widget.files!.files[firstPage!.token]!.firstOrNull?.id
         : null;
     return CustomScrollView(
       controller: controller,

lib/components/gallery_info_desktop.dart

@@ -59,9 +59,12 @@ class GalleryInfoDesktop extends StatelessWidget {
             child: Row(children: [
               Expanded(
                   flex: 3,
-                  child: Padding(padding: const EdgeInsets.only(right: 8.0),
-                    child: Thumbnail(gData.pages.first,
-                      fileId: fileId, gid: gData.meta.gid))),
+                  child: Padding(
+                      padding: const EdgeInsets.only(right: 8.0),
+                      child: gData.pages.isNotEmpty
+                          ? Thumbnail(gData.pages.first,
+                              fileId: fileId, gid: gData.meta.gid)
+                          : Container())),
               Expanded(
                   flex: 7,
                   child: Column(

lib/components/thumbnail_gridview.dart

@@ -23,7 +23,7 @@ class ThumbnailGridView extends StatelessWidget {
         itemBuilder: (context, index) {
           final page = npages[index]!;
           final fileId =
-              files != null ? files!.files[page.token]!.first.id : null;
+              files != null ? files!.files[page.token]!.firstOrNull?.id : null;
           final key = Key("thumbnail$gid-${page.index}");
           return Container(
               padding: const EdgeInsets.all(4),

lib/dialog/task_page.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_gen/gen_l10n/app_localizations.dart';
 import 'package:go_router/go_router.dart';
@@ -89,13 +90,42 @@ class _TaskPage extends State<TaskPage> {
     final maxWidth = MediaQuery.of(context).size.width;
     final endIndent = maxWidth < 400 ? 5.0 : 10.0;
     final indent = endIndent + 70;
+    final allowLink = task.base.gid != 0 &&
+        (typ != TaskType.download ||
+            task.status == TaskStatus.running ||
+            task.status == TaskStatus.finished);
+    String? title;
+    if (typ == TaskType.download && tasks.meta.containsKey(task.base.gid)) {
+      title = tasks.meta[task.base.gid]!.preferredTitle;
+    }
+    final cs = Theme.of(context).colorScheme;
     return Column(
       children: [
         _KeyValue(i18n.taskId, widget.id.toString(), fontSize: 16),
         Divider(indent: indent, endIndent: endIndent),
         _KeyValue(i18n.taskType, typ.text(context), fontSize: 16),
         Divider(indent: indent, endIndent: endIndent),
-        _KeyValue(i18n.gid, gid, fontSize: 16),
+        Row(children: [
+          SizedBox(
+              width: 80,
+              child: Center(
+                  child: Text(i18n.gid,
+                      textAlign: TextAlign.center,
+                      style: TextStyle(color: cs.primary, fontSize: 16)))),
+          Expanded(
+              child: allowLink
+                  ? SelectableText.rich(TextSpan(
+                      text: gid,
+                      style: TextStyle(color: cs.secondary, fontSize: 16),
+                      mouseCursor: SystemMouseCursors.click,
+                      recognizer: TapGestureRecognizer()
+                        ..onTap = () {
+                          context.push("/gallery/${task.base.gid}",
+                              extra: GalleryPageExtra(title: title));
+                        }))
+                  : SelectableText(gid,
+                      style: TextStyle(color: cs.secondary, fontSize: 16))),
+        ]),
         task.base.token.isEmpty
             ? Container()
             : Divider(indent: indent, endIndent: endIndent),
@@ -324,8 +354,12 @@ class _TaskPage extends State<TaskPage> {
     final indent = endIndent + 70;
     return Column(key: ValueKey("task_detail_meta_${widget.id}"), children: [
       _KeyValue(i18n.title2, meta.title, fontSize: 16),
-      Divider(indent: indent, endIndent: endIndent),
-      _KeyValue(i18n.titleJpn, meta.titleJpn, fontSize: 16),
+      meta.titleJpn.isNotEmpty
+          ? Divider(indent: indent, endIndent: endIndent)
+          : Container(),
+      meta.titleJpn.isNotEmpty
+          ? _KeyValue(i18n.titleJpn, meta.titleJpn, fontSize: 16)
+          : Container(),
       Divider(indent: indent, endIndent: endIndent),
       _KeyValue(i18n.category, meta.category, fontSize: 16),
       Divider(indent: indent, endIndent: endIndent),