Add extra test for stale entity references

ext/dom/tests/entity_reference_stale_03.phpt

@@ -0,0 +1,34 @@
+--TEST--
+Entity references with stale entity declaration 03
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+foreach (['firstChild', 'lastChild', 'textContent', 'childNodes'] as $prop) {
+    $dom = DOM\XMLDocument::createFromString(<<<XML
+    <!DOCTYPE foo [
+    <!ENTITY foo "bar">
+    ]>
+    <foo>&foo;</foo>
+    XML);
+
+    $ref = $dom->documentElement->firstChild;
+    $decl = $ref->firstChild;
+
+    $nodes = $ref->childNodes;
+    $dom->removeChild($dom->doctype);
+    unset($decl);
+
+    var_dump($ref->$prop);
+}
+
+?>
+--EXPECT--
+NULL
+NULL
+NULL
+object(DOM\NodeList)#1 (1) {
+  ["length"]=>
+  int(0)
+}