Only navigate to new/last draft on launch on macOS

This is causing the app to crash on launch when there are no existing posts, so we’re going to remove it for now while we investigate.

Shared/WriteFreely_MultiPlatformApp.swift

@@ -152,11 +152,13 @@ struct WriteFreely_MultiPlatformApp: App {
     }
 
     private func showLastDraftOrCreateNewLocalPost() {
+        #if os(macOS)
         if model.editor.lastDraftURL != nil {
             self.model.selectedPost = model.editor.fetchLastDraftFromAppStorage()
         } else {
             createNewLocalPost()
         }
+        #endif
     }
 
     private func createNewLocalPost() {