Quick fix for sub-orchestration gRPC serialization issue (#149)

Author: cgillum

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Updates
 
 * Synchronous reads for improved performance for large payloads ([#134](https://github.com/microsoft/durabletask-mssql/pull/134)) - contributed by [@bhugot](https://github.com/bhugot)
+* Fix for sub-orchestration handling over gRPC ([#149](https://github.com/microsoft/durabletask-mssql/pull/149))
 
 ## v1.1.0
 

src/DurableTask.SqlServer/SqlUtils.cs

@@ -127,7 +127,7 @@ public static HistoryEvent GetHistoryEvent(this DbDataReader reader, bool isOrch
                     historyEvent = new SubOrchestrationInstanceCreatedEvent(eventId)
                     {
                         Input = GetPayloadText(reader),
-                        InstanceId = null, // TODO
+                        InstanceId = "", // Placeholder - shouldn't technically be needed (adding it requires a SQL schema change)
                         Name = GetName(reader),
                         Version = null,
                     };