Fix some dark mode issue

src/Message.js

@@ -84,6 +84,7 @@ export class MessageViewer extends PureComponent {
     else if (this.state.loading_status === 'done')
       return (
         <>
+          <div className="box">
             <br />
             <p>
               最近一次重置 <Time stamp={this.state.start_time} short={false} />
@@ -122,7 +123,6 @@ export class MessageViewer extends PureComponent {
                 </span>
               ))}
             </div>
-          <br />
             <div>
               当前候选管理员:
               {this.state.candidate_list.map((admin) => (
@@ -131,6 +131,7 @@ export class MessageViewer extends PureComponent {
                 </span>
               ))}
             </div>
+          </div>
           {this.state.msg.map((msg) => (
             <div className="box" key={msg.type + msg.timestamp}>
               <div className="box-header">