Add pop-up warning when adding Scene on Tileset if Scene uses said resource

[SatLess]

Adding scenes on the Tileset resource is handy, especially when it is reusable, however it can cause unforeseen issues. E.g: you have a tile.res which both SceneA and SceneB use. You would like to instanciate the latter into SceneA by using the tileset. By adding SceneB into the resource, it creates a paradox (adding SceneB into the same resource it is used to instanciate it), and either the tiles for A or B gets deleted. I suggest adding a warning whenever this situation occurs, in order to make Godot feel more reliable and less error-prone.

[AThousandShips]

This sounds like a general circular reference limitation, which happens in many other places, and it's not easy to discover at times

[SatLess]

Agreed. I still believe there should be a way to prevent this so less of it happens.