TD-3838 Returns null int instead of zero and comments id manipulation code

Author: kevwhitt-hee

DigitalLearningSolutions.Data/DataServices/CourseContentService.cs

@@ -269,13 +269,13 @@ FROM Sessions AS S1 WITH (NOLOCK)
         {
             try
             {
-                return connection.QueryFirst<int>(
+                return connection.QueryFirst<int?>(
                     @"SELECT COALESCE((SELECT ProgressID 
 					FROM Progress
                     WHERE CandidateID = @candidateId
                       AND CustomisationID = @customisationId
                       AND SystemRefreshed = 0
-                      AND RemovedDate IS NULL), 0) AS ProgressId",
+                      AND RemovedDate IS NULL), NULL) AS ProgressId",
                     new { candidateId, customisationId }
                 );
             }

DigitalLearningSolutions.Web/Controllers/LearningMenuController/LearningMenuController.cs

@@ -85,10 +85,11 @@ public IActionResult Index(int customisationId)
                 var sectionId = courseContent.Sections.First().Id;
                 return RedirectToAction("Section", "LearningMenu", new { customisationId, sectionId });
             }
-            if (UniqueIdManipulationDetected(candidateId, customisationId))
-            {
-                return RedirectToAction("StatusCode", "LearningSolutions", new { code = 404 });
-            }
+            // Unique Id Manipulation Detection is being disabled as part of work on TD-3838 - a bug created by its introduction
+            //if (UniqueIdManipulationDetected(candidateId, customisationId))
+            //{
+            //    return RedirectToAction("StatusCode", "LearningSolutions", new { code = 404 });
+            //}
             var progressId = courseContentService.GetOrCreateProgressId(candidateId, customisationId, centreId);
             if (progressId == null)
             {
@@ -97,6 +98,7 @@ public IActionResult Index(int customisationId)
                     $"Candidate id: {candidateId}, customisation id: {customisationId}, centre id: {centreId}");
                 return RedirectToAction("StatusCode", "LearningSolutions", new { code = 404 });
             }
+
             if (sessionService.StartOrUpdateDelegateSession(candidateId, customisationId, HttpContext.Session) > 0)
             {
                 courseContentService.UpdateProgress(progressId.Value);