Create a custom component and then drop it on a call flow. Then delete the custom component from project explorer. The component ends up staying on the call flow where you dropped it, even though it has been deleted. If you double click on it in the call flow the VAD throws an error because it can't find the files. You probably want to warn when a component is deleted, whether or not it is currently in use on any call flows in the project, before deleting it.