Fixes issues with type check.

Author: ryasmi

src/Blueprint.php

@@ -69,16 +69,16 @@ public function validate() {
   }
 
   public function setProp($prop_key, $prop_value) {
-    if (gettype($new_value) !== 'object') {
-      return null;
+    if (gettype($this->value) !== 'object') {
+      return $this;
     }
 
     $this->value->setProp($prop_key, $prop_value);
     return $this;
   }
 
   public function getProp($prop_key) {
-    if (gettype($new_value) !== 'object') {
+    if (gettype($this->value) !== 'object') {
       return null;
     }