Merge pull request #90 from jsampedro77/fix-entity-to-string

Fix entities __toString method by making sure they won't return null.

Author: slashfan

Entity/Email.php

@@ -121,7 +121,7 @@ public function __construct()
      */
     public function __toString()
     {
-        return $this->reference;
+        return $this->reference?:'';
     }
 
     /**

Entity/EmailTranslation.php

@@ -114,7 +114,7 @@ public function __construct($lang = null)
      */
     public function __toString()
     {
-        return $this->lang;
+        return $this->lang?:'';
     }
 
     /**

Entity/Layout.php

@@ -199,7 +199,7 @@ public function getTranslation($lang)
      */
     public function __toString()
     {
-        return $this->reference;
+        return $this->reference?:'';
     }
 
     /**

Entity/LayoutTranslation.php

@@ -81,7 +81,7 @@ public function __construct($lang = null)
      */
     public function __toString()
     {
-        return $this->lang;
+        return $this->lang?:'';
     }
 
     /**