fix: checkmark background color lost for unselected poll issue

Mastodon/Scene/Share/View/Content/PollOptionView+Configuration.swift

@@ -101,7 +101,9 @@ extension PollOptionView {
             .receive(on: DispatchQueue.main)
             .sink { [weak self] theme in
                 guard let self = self else { return }
-                self.checkmarkBackgroundView.backgroundColor = theme.tertiarySystemBackgroundColor
+                self.checkmarkBackgroundView.backgroundColor = UIColor(dynamicProvider: { trailtCollection in
+                    return trailtCollection.userInterfaceStyle == .light ? .white : theme.tableViewCellSelectionBackgroundColor
+                })
             }
             .store(in: &disposeBag)
     }