fix 快应用章节报错

app/Http/Controllers/QuickApp/Book/ChapterController.php

@@ -127,7 +127,7 @@ class ChapterController extends BaseController
         $bid    = BookService::decodeBidStatic($bid);
         //获取图书信息
         $book_info = BookConfigService::getBookById($bid);
-        if (empty($book_info))
+        if (!$book_info)
             return response()->error('QAPP_SYS_ERROR');
         if($this->distribution_channel_id == 7477 && $bid == 13765){
             $book_info->is_on_shelf = 2;