IG/GG: clicking in empty graph space should also deselect previz

[mennovu]

Clicking anywhere in the graph region that's not a node deselects the current node, but selected previz pins remain selected - would expect that selection to be dropped as well. Otherwise the user has to either search for the current previz pin and deselect it or select another pin and immediately deselect it.

[albertosantini]

If you are using an extension, you should fill the issue in their support.