DispatchPendingWorkflowAsync method returns NullReferenceException

_Elsa version : 2.6.0_

Hello,

Excuse me for the long post that's coming.
I've been trying to use the method **DispatchPendingWorkflowAsync** and **CollectAndExecuteWorkflowsAsync** from the workflow launchpad service.
I am running 2 simple workflows (as in starting one -> it finishes; starting the second -> it finishes; and so on in random order)
For every of these 2 workflows I have a bookmark that gets executed in my code by calling the method CollectAndExecuteWorkflowsAsync.

First thing I observed after the method CollectAndExecuteWorkflowsAsync is called is that sometimes it created another new instance of the other workflow. All other instances were in status 2 - finished, no other workflow in pending.
So if I started workflow 1 -> CollectAndExecuteWorkflowsAsync is called -> CollectedWorkflows result gives 2 workflows (an instance for workflow 1 and a new instance for workflow 2) -> workflow 1 finished and a new instance with workflow 2 is created
**This is the code that I executed**:
```
var templateMessageContext = new WorkflowsQuery(nameof(SendMessage), new SendTemplateMessageBookmark(), workflowInstance.CorrelationId, workflowInstance.Id);
var templateMessageWorkflowInput = new WorkflowInput(message);
var collectedWorkflow = await _workflowLaunchpad.CollectAndExecuteWorkflowsAsync(templateMessageContext, templateMessageWorkflowInput, cancellationToken);
```

So after this, I started looking into the launchpad service and I tested a similar method, **DispatchPendingWorkflowAsync**:
```
var collectedWorkflow = new CollectedWorkflow(workflowInstance.Id, null);
await _workflowLaunchpad.DispatchPendingWorkflowAsync(collectedWorkflow, templateMessageWorkflowInput, cancellationToken);
```

then I received this exception at execution:
```
---> (Inner Exception #1) System.NullReferenceException: Object reference not set to an instance of an object.
at Elsa.Services.Workflows.WorkflowRunner.ResumeWorkflowAsync(WorkflowExecutionContext workflowExecutionContext, IActivityBlueprint activity, CancellationToken cancellationToken)
at Elsa.Services.Workflows.WorkflowRunner.RunWorkflowInternalAsync(WorkflowExecutionContext workflowExecutionContext, String activityId, CancellationToken cancellationToken)
at Elsa.Services.Workflows.WorkflowRunner.RunWorkflowAsync(IWorkflowBlueprint workflowBlueprint, WorkflowInstance workflowInstance, String activityId, WorkflowInput input, CancellationToken cancellationToken)
at Elsa.Services.Workflows.WorkflowResumer.ResumeWorkflowAsync(WorkflowInstance workflowInstance, String activityId, WorkflowInput input, CancellationToken cancellationToken)
at Elsa.Services.Workflows.WorkflowInstanceExecutor.ExecuteAsync(WorkflowInstance workflowInstance, String activityId, WorkflowInput input, CancellationToken cancellationToken)
at Elsa.Decorators.LockingWorkflowInstanceExecutor.ExecuteAsync(String workflowInstanceId, String activityId, WorkflowInput input, CancellationToken cancellationToken)
at Elsa.Decorators.LockingWorkflowInstanceExecutor.ExecuteAsync(String workflowInstanceId, String activityId, WorkflowInput input, CancellationToken cancellationToken)
at Elsa.Decorators.LockingWorkflowInstanceExecutor.ExecuteAsync(String workflowInstanceId, String activityId, WorkflowInput input, CancellationToken cancellationToken)
at Elsa.Services.Dispatch.Consumers.ExecuteWorkflowInstanceRequestConsumer.Handle(ExecuteWorkflowInstanceRequest message)
at Rebus.Pipeline.Receive.HandlerInvoker`1.Invoke()
at Rebus.Pipeline.Receive.DispatchIncomingMessageStep.Process(IncomingStepContext context, Func`1 next)
at Rebus.Sagas.LoadSagaDataStep.Process(IncomingStepContext context, Func`1 next)
at Rebus.Pipeline.Receive.ActivateHandlersStep.Process(IncomingStepContext context, Func`1 next)
at Rebus.Pipeline.Receive.HandleRoutingSlipsStep.Process(IncomingStepContext context, Func`1 next)
at Rebus.Pipeline.Receive.DeserializeIncomingMessageStep.Process(IncomingStepContext context, Func`1 next)
at Rebus.DataBus.ClaimCheck.HydrateIncomingMessageStep.Process(IncomingStepContext context, Func`1 next)
at Rebus.Pipeline.Receive.HandleDeferredMessagesStep.Process(IncomingStepContext context, Func`1 next)
at Rebus.Retry.FailFast.FailFastStep.Process(IncomingStepContext context, Func`1 next)
at Rebus.Retry.Simple.SimpleRetryStrategyStep.DispatchWithTrackerIdentifier(Func`1 next, String identifierToTrackMessageBy, ITransactionContext transactionContext, String messageId, String secondLevelMessageId)<---
```

I've been trying some debugging on it and the method _workflowInstanceDispatcher.DispatchAsync is giving the error.

Second observation (but maybe I'm wrong), I see that in Elsa 2.6.0 the CollectedWorkflow constructor has only 2 arguments. In the workflow launchpad service, CollectedWorkflow has 3 arguments.

Regardless of my untrained observations, could you please guide me towards some solution of this problem? Let me know if you need more information.

Thank you !!