#19109: Fixing NRE when deleting tasks not associated with content items

Work Item: 19109

--HG--
branch : 1.x

src/Orchard.Web/Core/Scheduling/Services/ScheduledTaskManager.cs

@@ -56,7 +56,8 @@ namespace Orchard.Core.Scheduling.Services {
         }
 
         public void DeleteTasks(ContentItem contentItem, Func<IScheduledTask, bool> predicate = null ) {
-            var tasks = _repository
+            // if contentItem is null, all tasks are used
+            var tasks = contentItem == null ? _repository.Table : _repository
                 .Fetch(x => x.ContentItemVersionRecord.ContentItemRecord == contentItem.Record);
 
             foreach (var task in tasks) {