NSPasteboard Crashes When Handling File Promises

Wade Tregaskis: NSPasteboard mutates itself simultaneously from the main thread and the global concurrent Dispatch pool, w.r.t. to its internal type cache. This is surprisingly trivial to reproduce (sample code below) by just dropping, e.g. a file promise (such as by opening a PNG in Preview, revealing the thumbnails sidebar, and then dragging the thumbnail [ ]