修复清空按钮在暗夜模式下显示为灰色

Note/ClipInboxViewController.swift

@@ -96,10 +96,16 @@ class ClipInboxViewController: UIViewController {
         let isEmpty = clips.isEmpty
         emptyLabel.isHidden = !isEmpty
         tableView.isHidden = isEmpty
-        navigationItem.rightBarButtonItem?.isEnabled = !isEmpty
     }
 
     @objc private func didTapClearButton() {
+        guard !clips.isEmpty else {
+            let alert = UIAlertController(title: "提示", message: "收集箱为空，没有可清空的内容。", preferredStyle: .alert)
+            alert.addAction(UIAlertAction(title: "确定", style: .default))
+            present(alert, animated: true)
+            return
+        }
+
         let alert = UIAlertController(
             title: "清空收集箱",
             message: "确定要删除所有保存的文案吗？此操作不可撤销。",