fixed: linq method unsupported

src/Hotline.Api/Controllers/OrderController.cs

@@ -2188,7 +2188,7 @@ public class OrderController : BaseController
             .WhereIF(dto.IsHandled.HasValue, d => handleStatuses.Contains(d.Status))
             .WhereIF(!string.IsNullOrEmpty(dto.Keyword),
                 d => d.No.Contains(dto.Keyword!) || d.Title.Contains(dto.Keyword!))
-            .Where(d => !d.IsSigned() || d.SignerId == _sessionContext.RequiredUserId)
+            .Where(d => string.IsNullOrEmpty(d.SignerId) || d.SignerId == _sessionContext.RequiredUserId)
             .OrderByDescending(d => d.ExpiredTime)
             .ToPagedListAsync(dto, HttpContext.RequestAborted);