Tapestry 5.3.6 JSONObject No null checking leads to NPE in Palette component

*java.lang.NullPointerException* :

* at
org.apache.tapestry5.json.JSONObject.printValue(JSONObject.java:887)
* at org.apache.tapestry5.json.JSONArray.print(JSONArray.java:436)
* at
org.apache.tapestry5.json.JSONCollection.toString(JSONCollection.java:47)

* at
org.apache.tapestry5.json.JSONCollection.toString(JSONCollection.java:63)

* at
org.apache.tapestry5.corelib.components.Palette.beginRender(Palette.java:393)

There is no null checking in printValue(JSONPrintSession session, Object
value)

Adding :

if (NULL.equals(value))

session.print(NULL.toString());
return;

solves the problem.