[bugfix] Avoid ClassCastException when the attribute was constructed directly

Author: adamretter

exist-core/src/main/java/org/exist/dom/memtree/AttrImpl.java

@@ -124,7 +124,11 @@ public void setTextContent(final String textContent) throws DOMException {
 
     @Override
     public Element getOwnerElement() {
-        return (Element) document.getNode(document.attrParent[nodeNumber]);
+        final Node node = document.getNode(document.attrParent[nodeNumber]);
+        if (node != null && node.getNodeType() == Node.ELEMENT_NODE) {
+            return (Element) node;
+        }
+        return null;
     }
 
     @Override