Fixed bug in WP_Option

@@ -11,15 +11,18 @@ class WP_Option implements ArrayAccess, Countable {
         $this->_ns   = $ns;
         $this->_data = get_option($ns);
 
+        $changed = false;
         if (is_array($defaults)) {
-            foreach ($this->_data as $key => $val) {
-                $defaults[$key] = $val;
+            foreach ($defaults as $key => $val) {
+                if (!isset($this->_data[$key])) {
+                    $this->_data[$key] = $val;
+                    $changed = true;
+                }
             }
+        }
 
-            if ($this->_data != $defaults) {
-                $this->_data = $defaults;
-                $this->save();
-            }
+        if ($changed) {
+            $this->save();
         }
     }