opt video bottomsheet

Signed-off-by: dom <githubaccount56556@proton.me>

lib/pages/video/widgets/header_control.dart

@@ -1247,7 +1247,7 @@ class HeaderControlState extends State<HeaderControl>
   /// 字幕设置
   void showSetSubtitle() {
     showBottomSheet(
-      padding: isFullScreen ? 70 : null,
+      padding: () => isFullScreen ? const .only(bottom: 70) : .zero,
       (context, setState) {
         final theme = Theme.of(context);