NullPointerException at org.zkoss.zul.Selectbox.onInitRenderNow. got this error for selectbox in zk framework - drop-down-menu

Question

I got an error for SelectBox in the ZK framework.
Please check my code
Zul side code:
<?import com.myfarmony.farmpro.newinterfacedesign.viewmodel.DashboardModel ?>
<zk xmlns:h="native" xmlns:w="client">
<div apply="org.zkoss.bind.BindComposer" viewModel="#id('vm') #init('DashboardModel')" sclass="br-mainpanel">
<selectbox model="#load(vm.soldBy)" width="110px">
<template name="model">
${each}
</template>
</selectbox>
</div>
</zk>
Java controller side code:
private ListModelList<String> soldBy = new ListModelList<String>();
soldBy = new ListModelList<String>() {{
add(new String("All"));
add(new String("Mr. Jaydeep Dhameliya"));
add(new String("Miss. Shivani Shah"));
add(new String("Mr. Rushi Parikh"));
add(new String("ALL"));
}};
soldBy.addToSelection("All");
I got below error and my zk version is 8.5 and I did google for this error but I didn't get any proper solution.
Jan 10, 2020 7:16:19 PM org.zkoss.zk.ui.impl.UiEngineImpl handleError
SEVERE: java.lang.NullPointerException
at org.zkoss.zul.Selectbox.onInitRenderNow(Selectbox.java:300)
at org.zkoss.zul.Selectbox.onInitRender(Selectbox.java:282)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:3143)
at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:3074)
at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:138)
at org.zkoss.zk.ui.impl.UiEngineImpl.processEvent(UiEngineImpl.java:1846)
at org.zkoss.zk.ui.impl.UiEngineImpl.process(UiEngineImpl.java:1618)
at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage0(UiEngineImpl.java:548)
at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage(UiEngineImpl.java:369)
at org.zkoss.zk.ui.http.DHtmlLayoutServlet.process(DHtmlLayoutServlet.java:211)
at org.zkoss.zk.ui.http.DHtmlLayoutServlet.doGet(DHtmlLayoutServlet.java:137)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:749)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:487)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:412)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:339)
at com.myfarmony.farmpro.servlet.NewInterfaceServlet.doGet(NewInterfaceServlet.java:17)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)

Answer 1

I just ran your code in a zkfiddle (http://zkfiddle.org/sample/jgfbe8/1-NPE-selectbox) and it just works without any errors.
Maybe this already helps you to put your code in the correct place, or you can update the zkfiddle and add what's missing to produce the error.