Stack overflow exception from VisualizerMapping with second VisualizerMapping as input

[RoboDoig]

While investigating #1591 I noticed that creating this workflow is possible in the editor:

When run this results in a terminating crash from a stack overflow exception, presumably due to a cyclical dependency.

[RoboDoig]

Looked into this a bit more, the issue comes from entering an infinite recursive call in LayoutHelper.GetMashupArguments. For example in this case, the Int mapping source argument will be passed on every recursive call.

I can't think of any situation where you would want to combine visualizers as in the workflow example above as the information is redundant. In that case the fix may be just to disallow visualizer combinations where the data source is the same for visualizers in the combination.