added some error handler

application/libraries/OptionsLib.php

@@ -131,7 +131,11 @@ class OptionsLib {
 
         $logo = $CI->Themes_model->get_logo_from_theme($theme, $logo_location);
 
-        return $logo;
+        if ($logo != null) {
+            return $logo;
+        } else {
+            return 'no_logo_found';
+        }
     }
 
 }

application/models/Themes_model.php

@@ -64,6 +64,7 @@ class Themes_model extends CI_Model {
 	
 			return ($value !== null) ? (string) $value : null;
 		} else {
+			log_message('error', 'get_logo_from_theme failed');
 			return null;
 		}
 	}