 			return
 		}
 		
-		let container = selectedContainer()!
+		guard let container = selectedContainer() else { return }
 		AddWebFeedDefaultContainer.saveDefaultContainer(container)
 
 		delegate?.addFeedWindowController(self, userEnteredURL: url, userEnteredTitle: userEnteredTitle, container: container)

private extension AddWebFeedWindowController {
	
	private func updateUI() {
		addButton.isEnabled = urlTextField.stringValue.mayBeURL
	}

	func cancelSheet() {

	}

	func selectedContainer() -> Container? {
		guard folderPopupButton.selectedItem?.isEnabled ?? false else { return nil }
		return folderPopupButton.selectedItem?.representedObject as? Container
	}
}
