Merge branch 'cd299' into dev

src/Hotline.Share/Dtos/Order/SendBackDto.cs

@@ -113,8 +113,12 @@ namespace Hotline.Share.Dtos.Order
 		public double SendBackTimeDifference => GetSendBackTimeDifference();
 
 		public double GetSendBackTimeDifference() {
-			TimeSpan? timeDifference = CreationTime - WorkflowStepSendBackCrTime;
-			return Math.Round(timeDifference.Value.TotalMinutes / 60, 1);
+			if (WorkflowStepSendBackCrTime.HasValue)
+			{
+				TimeSpan? timeDifference = CreationTime - WorkflowStepSendBackCrTime;
+				return Math.Round(timeDifference.Value.TotalMinutes / 60, 1);
+			}
+			return 0;
 		}