Fix DOM bug test case

The behaviour now displayed seems correct compared to the previous one

Author: Girgias

ext/dom/tests/bug47849.phpt

@@ -19,4 +19,4 @@ echo $aDOM->saveXML();
 ?>
 --EXPECT--
 <?xml version="1.0"?>
-<r:root xmlns:r="urn::root"><data xmlns="urn::data"/></r:root>
+<r:root xmlns:r="urn::root"><data xmlns="urn::data">aaa</data></r:root>