Don't close send files box by outside click.

Telegram/SourceFiles/history/history_widget.cpp

@@ -4250,7 +4250,9 @@ bool HistoryWidget::confirmSendingFiles(
 	}));
 
 	ActivateWindowDelayed(controller());
-	Ui::show(std::move(box));
+	const auto shown = Ui::show(std::move(box));
+	shown->setCloseByOutsideClick(false);
+
 	return true;
 }