**This will not cause any issues in vanilla since this transition is never officially used.**
While PlayGameConfig does check if an empty resource was passed, it does not check if the resource is actually a scenario config or even exists at all.
Adding a simple resource validity check would make the method safer to use for modders out of the box:
For example, the resource (scenario config) could be loaded from the name, checked for validity and and finally casted to the mission header class.