invalid compiler output. invalid collection index: childwidgets

I'm testing Outsystems. I get an error when compiling a test application.

following:

Internal Error
Invalid compiler output.
Invalid Collection Index: ChildWidgets
Exception Details:
[1] System.InvalidOperationException: Invalid Collection Index: ChildWidgets
   at OutSystems.HubEdition.Compiler.AbstractObject.GetChildCollection(CollectionIndex collectionIndex)
   at OutSystems.HubEdition.Compiler.WebWidgets.Placeholder.GetChildCollection(CollectionIndex collectionIndex)
   at OutSystems.HubEdition.Compiler.CompoundKeyResolver.GetObjectResolver.Visit(ChildCompoundKey childCompoundKey)
   at OutSystems.Oml.CompoundKeys.ChildCompoundKey.Accept(ICompoundKeyVisitor visitor)
   at OutSystems.HubEdition.Compiler.CompoundKeyResolver.TryGetObject(CompoundKey key, AbstractObject relativeTo)
   at OutSystems.HubEdition.Compiler.CompoundKeyResolver.GetObjectResolver.Visit(ChildCompoundKey childCompoundKey)
   at OutSystems.Oml.CompoundKeys.ChildCompoundKey.Accept(ICompoundKeyVisitor visitor)
   at OutSystems.HubEdition.Compiler.CompoundKeyResolver.TryGetObject(CompoundKey key, AbstractObject relativeTo)
   at OutSystems.HubEdition.Compiler.CompoundKeyResolver.GetObject(CompoundKey key, AbstractObject relativeTo)
   at OutSystems.HubEdition.Compiler.Expressions.AbstractExpression.ResolveRef(AbstractObject& refCache, CompoundKey& refKey, String nameRef)
   at OutSystems.HubEdition.Compiler.Expressions.CompoundExpressions.CompoundWidgetId.get_fieldKey()
   at OutSystems.HubEdition.Compiler.Optimizer.IdentifierExpressionFieldCollector.processFieldExpression(IFieldExpression field)
   at OutSystems.HubEdition.Compiler.Optimizer.ExpressionIdentifierUsage.ExpressionIdentifierUsageFieldCollector.processFieldExpression(IFieldExpression field)
   at OutSystems.HubEdition.Compiler.Optimizer.IdentifierExpressionFieldVisitor..ctor(IIdentifierExpression exp)
   at OutSystems.HubEdition.Compiler.Optimizer.ExpressionIdentifierUsage.addIdentifierExpression(IIdentifierExpression expression, Boolean exitsScope)
   at OutSystems.HubEdition.Compiler.Expressions.CompoundExpressions.CompoundWidgetId.collectUsage(ExpressionIdentifierUsage identifiers, Boolean exitsScope)
   at OutSystems.HubEdition.Compiler.Expressions.CallFunction.collectUsage(ExpressionIdentifierUsage identifiers, Boolean exitsScope)
   at OutSystems.HubEdition.Compiler.Expressions.AbstractExpression.collectUsage(ExpressionIdentifierUsage identifiers, AbstractExpression subExpr)
   at OutSystems.HubEdition.Compiler.Optimizer.OptimizerNodeUsage.getExpressionUsage(AbstractExpression exp, AbstractExpression subExpr)
   at OutSystems.HubEdition.Compiler.Optimizer.OptimizerNodeUsage.setAsRead(AbstractExpression exp, AbstractExpression subExpr)
   at OutSystems.HubEdition.Compiler.Optimizer.OptimizerNodeUsage.setImplicitParametersListAsRead(IEnumerable`1 implicitParameters)
   at OutSystems.HubEdition.Compiler.Nodes.AbstractDataSet.collectUsage(OptimizerNodeUsage usage)
   at OutSystems.HubEdition.Compiler.Optimizer.OptimizerGraphs.OptimizerNodes.OptimizerActionNode.calculeUsage()
   at OutSystems.HubEdition.Compiler.Optimizer.OptimizerUtils.removeEmptyNodes(IOptimizableGraph graph)
   at OutSystems.HubEdition.Compiler.Optimizer.ViewState.NodeViewState..ctor(IServerScreenFlowNode screen)
   at OutSystems.HubEdition.Compiler.Interfaces.ServerScreenFlowNodeUtils.DefaultOptimize(IServerScreenFlowNode screenFlowNode, NodeViewState& viewState)
   at OutSystems.HubEdition.Compiler.Flows.WebFlow.Optimize()
   at OutSystems.HubEdition.Compiler.WebFlows.WebHandler.Dump(IEnumerable`1 webFlows)
   at OutSystems.HubEdition.Compiler.ESpace.Dump()
   at OutSystems.HubEdition.Compiler.Compiler.InnerCompileEspace(ESpace eSpace, CompilationContext context)
   at OutSystems.HubEdition.Compiler.Utils.CompilerUtils.TrapExceptionsInContext(Action action, CompilationContext context)

Hi Akira,

You should contact OutSystems Support to report this error. Then, try to see what causes it, by incrementally adding things then Publishing after each step, until you hit the error.