diff --git a/application/classes/modules/topic/entity/Topic.entity.class.php b/application/classes/modules/topic/entity/Topic.entity.class.php
index e57cd870..24f4346f 100644
--- a/application/classes/modules/topic/entity/Topic.entity.class.php
+++ b/application/classes/modules/topic/entity/Topic.entity.class.php
@@ -154,7 +154,7 @@ class ModuleTopic_EntityTopic extends Entity
      */
     public function ValidateBlogs($sValue, $aParams)
     {
-        if (is_string($sValue)) {
+        if ($sValue and is_string($sValue)) {
             $sValue = explode(',', $sValue);
         }
         if (!$sValue or !is_array($sValue)) {