Use black avatar color for collect photos

lib/ui/sharing/user_avator_widget.dart

@@ -26,10 +26,13 @@ class UserAvatarWidget extends StatelessWidget {
     final displayChar = (user.name == null || user.name!.isEmpty)
         ? ((user.email.isEmpty) ? " " : user.email.substring(0, 1))
         : user.name!.substring(0, 1);
-    final randomColor = colorScheme.avatarColors[
-        (user.id ?? 0).remainder(colorScheme.avatarColors.length)];
-    final Color decorationColor =
-        ((user.id ?? -1) == currentUserID) ? Colors.black : randomColor;
+    Color decorationColor;
+    if (user.id == null || user.id! <= 0 || user.id == currentUserID) {
+      decorationColor = Colors.black;
+    } else {
+      decorationColor = colorScheme
+          .avatarColors[(user.id!).remainder(colorScheme.avatarColors.length)];
+    }
 
     final avatarStyle = getAvatarStyle(context, type);
     final double size = avatarStyle.item1;

lib/ui/viewer/file/thumbnail_widget.dart

@@ -10,7 +10,6 @@ import 'package:photos/db/files_db.dart';
 import 'package:photos/db/trash_db.dart';
 import 'package:photos/events/files_updated_event.dart';
 import 'package:photos/events/local_photos_updated_event.dart';
-import 'package:photos/extensions/string_ext.dart';
 import 'package:photos/models/collection.dart';
 import 'package:photos/models/file.dart';
 import 'package:photos/models/file_type.dart';
@@ -128,11 +127,10 @@ class _ThumbnailWidgetState extends State<ThumbnailWidget> {
           );
         } else if (widget.file!.pubMagicMetadata!.uploaderName != null) {
           contentChildren.add(
-            // Use uploadName hashCode as userID so that different uploader
-            // get avatar color
+            // Use -1 as userID for enforcing black avatar color
             OwnerAvatarOverlayIcon(
               User(
-                id: widget.file!.pubMagicMetadata!.uploaderName.sumAsciiValues,
+                id: -1,
                 email: '',
                 name: widget.file!.pubMagicMetadata!.uploaderName,
               ),