fix warning on undefined lang

classes/cronlog.class.php

@@ -78,7 +78,7 @@ class cronlog {
             $this->_aSkipJoblogs = isset($aCfgTemp['aHidelogs']) && is_array($aCfgTemp['aHidelogs']) ? $aCfgTemp['aHidelogs'] : $this->_aSkipJoblogs;        
             $this->_aInstances = isset($aCfgTemp['instances']) ? $aCfgTemp['instances'] : [];
 
-            $this->_sLang=$aCfgTemp['lang'] ? $aCfgTemp['lang'] : 'en-en';
+            $this->_sLang=isset($aCfgTemp['lang']) && $aCfgTemp['lang'] ? $aCfgTemp['lang'] : 'en-en';
             $this->_aLang=$aCfgTemp=include(__DIR__.'/../config/lang_'.$this->_sLang.'.php');
         }
         $this->_sDataDir = str_replace("__APPDIR__", dirname(dirname(__FILE__)), $this->_sDataDir);