* add a fallback for none exist demo data sources.

module/ai/lang/en.php

@@ -379,6 +379,7 @@ $lang->ai->dataType->realStarted  = $lang->ai->dataType->datetime;
 $lang->ai->dataType->finishedDate = $lang->ai->dataType->datetime;
 
 $lang->ai->demoData            = new stdclass();
+$lang->ai->demoData->notExist  = 'The demo data does not exist for now.';
 $lang->ai->demoData->story     = array(
     'story' => array
     (

module/ai/lang/zh-cn.php

@@ -380,6 +380,7 @@ $lang->ai->dataType->realStarted  = $lang->ai->dataType->datetime;
 $lang->ai->dataType->finishedDate = $lang->ai->dataType->datetime;
 
 $lang->ai->demoData            = new stdclass();
+$lang->ai->demoData->notExist  = '暂无演示数据。';
 $lang->ai->demoData->story     = array(
     'story' => array
     (

module/ai/model.php

@@ -575,6 +575,8 @@ class aiModel extends model
      */
     public function generateDemoDataPrompt($module, $source)
     {
+        if(empty($this->lang->ai->demoData->$module)) return $this->lang->ai->demoData->notExist;
+
         $sources = explode(',', $source);
         $sources = array_filter($sources);