Fix parse method return arguments null (chriskacerguis#744)

* fix cross site to option request error 

cross site request first can use option http method.
but use `keys` authentication, authentication can fail

* Fix Parse error

Fix parse method return arguments null

Author: yuyaun

application/libraries/REST_Controller.php

@@ -475,6 +475,12 @@ public function __construct($config = 'rest')
         $this->request->body = NULL;
 
         $this->{'_parse_' . $this->request->method}();
+        
+        // Fix parse method return arguments null
+        if($this->{'_'.$this->request->method.'_args'} === null)
+        {
+            $this->{'_'.$this->request->method.'_args'} = [];
+        }
 
         // Now we know all about our request, let's try and parse the body if it exists
         if ($this->request->format && $this->request->body)