return done when the collection is empty (#313)

Co-authored-by: Dan Absher <DAbsher@columbiabank.com>

src/activities/Elsa.Activities.ControlFlow/Activities/ForEach.cs

@@ -48,6 +48,11 @@ namespace Elsa.Activities.ControlFlow.Activities
             var collection = await expressionEvaluator.EvaluateAsync(CollectionExpression, context, cancellationToken);
             var index = CurrentIndex;
 
+            if (collection.Count == 0)
+            {
+                return Done();
+            }
+
             if (index >= collection.Count)
             {
                 context.EndScope();