feat(metadata): add Jellyfin edit support

lib/utils/dialogs.dart

@@ -120,6 +120,7 @@ Future<String?> showTextInputDialog(
   TextInputType? keyboardType,
   List<TextInputFormatter>? inputFormatters,
   String? Function(String)? validator,
+  bool allowEmpty = false,
 }) {
   return showDialog<String>(
     context: context,
@@ -132,6 +133,7 @@ Future<String?> showTextInputDialog(
       keyboardType: keyboardType,
       inputFormatters: inputFormatters,
       validator: validator,
+      allowEmpty: allowEmpty,
     ),
   );
 }
@@ -237,6 +239,7 @@ class _TextInputDialog extends StatefulWidget {
   final TextInputType? keyboardType;
   final List<TextInputFormatter>? inputFormatters;
   final String? Function(String)? validator;
+  final bool allowEmpty;
 
   const _TextInputDialog({
     required this.title,
@@ -247,6 +250,7 @@ class _TextInputDialog extends StatefulWidget {
     this.keyboardType,
     this.inputFormatters,
     this.validator,
+    this.allowEmpty = false,
   });
 
   @override
@@ -260,7 +264,7 @@ class _TextInputDialogState extends State<_TextInputDialog>
 
   void _submit() {
     final text = _controller.text;
-    if (text.isEmpty) return;
+    if (text.isEmpty && !widget.allowEmpty) return;
     if (widget.validator != null && widget.validator!(text) != null) return;
     Navigator.pop(context, text);
   }