Jcrop Servlet Problem since ZK6.5

I've integrated Jcrop into my ZK project and everything worked fine with ZK5.0

Since I've updated to ZK6.5 following problem occurs.

Stacktrace from browser:

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

java.lang.NullPointerException servlet.ImageCrop.doGet(ImageCrop.java:37) javax.servlet.http.HttpServlet.service(HttpServlet.java:617) javax.servlet.http.HttpServlet.service(HttpServlet.java:717) note The full stack trace of the root cause is available in the Apache Tomcat/6.0.35 logs.

my code:

-> .jsp file

<form action="/CM/ImageServlet" method="get" target="_self" onsubmit="return checkCoords();"> <input type="hidden" id="x" name="l"/> <input type="hidden" id="y" name="t"/> <input type="hidden" id="w" name="w"/> <input type="hidden" id="h" name="h"/> <input type="submit" value="Bildausschnitt übernehmen"/> </form>

-> web.xml

<servlet>
    <servlet-name>ImageCrop</servlet-name>
    <servlet-class>servlet.ImageCrop</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>ImageCrop</servlet-name>
    <url-pattern>/ImageServlet</url-pattern>
</servlet-mapping>

-> java

public synchronized void doGet(HttpServletRequest req,
        HttpServletResponse res) throws IOException, ServletException {

    HttpSession session = req.getSession(true);

            //DO Something