Problemas com consulta no HQL

Boa tarde galera.
Recentemente iniciei meus estudo em Hibernate e estou enfrentando problemas com a cláusula “where” de HQL.
Preciso listar itens de um determinado pedido de compra.
Segue código e respectivo retorno.

@SuppressWarnings("unchecked")
	public List<ItemCompra> listarItensCompra(Integer pedido) {
		EntityManager entityManager = JPAUtil.getEntityManager();
		Query query = entityManager.createQuery("from ItemCompra where pedidoItemCompra= :pedido  Order By id");
		query.setParameter("pedido", pedido);
		return query.getResultList();
	}

public String salvar() {
new ItemCompraDao().salvar(itemCompra);
itensCompra = new ItemCompraDao().listarItensCompra(pedidoCompraBean.getUltimoPedido().getId());
itemCompra = new ItemCompra();
FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(“Item salvo com sucesso!”));
return “contapagar”;
}

    ADVERTÊNCIA: #{itemCompraBean.salvar}: java.lang.NullPointerException
    javax.faces.FacesException: #{itemCompraBean.salvar}: java.lang.NullPointerException
    	at com.sun.faces.application.ActionListenerImpl.processAction(Unknown Source)
    	at javax.faces.component.UICommand.broadcast(Unknown Source)
    	at javax.faces.component.UIViewRoot.broadcastEvents(Unknown Source)
    	at javax.faces.component.UIViewRoot.processApplication(Unknown Source)
    	at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(Unknown Source)
    	at com.sun.faces.lifecycle.Phase.doPhase(Unknown Source)
    	at com.sun.faces.lifecycle.LifecycleImpl.execute(Unknown Source)
    	at javax.faces.webapp.FacesServlet.service(Unknown Source)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    	at br.com.pesadao.filter.AutorizacaoFilter.doFilter(AutorizacaoFilter.java:62)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:475)
    	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
    	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624)
    	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:498)
    	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:796)
    	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1366)
    	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    	at java.lang.Thread.run(Unknown Source)
    Caused by: javax.faces.el.EvaluationException: java.lang.NullPointerException
    	at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(Unknown Source)
    	... 33 more
    Caused by: java.lang.NullPointerException
    	at br.com.pesadao.bean.ItemCompraBean.salvar(ItemCompraBean.java:38)
    	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    	at java.lang.reflect.Method.invoke(Unknown Source)
    	at org.apache.el.parser.AstValue.invoke(AstValue.java:247)
    	at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:267)
    	at com.sun.faces.facelets.el.TagMethodExpression.invoke(Unknown Source)
    	... 34 more

    jul 01, 2017 3:43:44 PM com.sun.faces.context.AjaxExceptionHandlerImpl handlePartialResponseError
    GRAVE: javax.faces.el.EvaluationException: java.lang.NullPointerException
    	at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(Unknown Source)
    	at com.sun.faces.application.ActionListenerImpl.processAction(Unknown Source)
    	at javax.faces.component.UICommand.broadcast(Unknown Source)
    	at javax.faces.component.UIViewRoot.broadcastEvents(Unknown Source)
    	at javax.faces.component.UIViewRoot.processApplication(Unknown Source)
    	at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(Unknown Source)
    	at com.sun.faces.lifecycle.Phase.doPhase(Unknown Source)
    	at com.sun.faces.lifecycle.LifecycleImpl.execute(Unknown Source)
    	at javax.faces.webapp.FacesServlet.service(Unknown Source)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    	at br.com.pesadao.filter.AutorizacaoFilter.doFilter(AutorizacaoFilter.java:62)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:475)
    	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
    	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624)
    	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:498)
    	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:796)
    	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1366)
    	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    	at java.lang.Thread.run(Unknown Source)
    Caused by: java.lang.NullPointerException
    	at br.com.pesadao.bean.ItemCompraBean.salvar(ItemCompraBean.java:38)
    	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    	at java.lang.reflect.Method.invoke(Unknown Source)
    	at org.apache.el.parser.AstValue.invoke(AstValue.java:247)
    	at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:267)
    	at com.sun.faces.facelets.el.TagMethodExpression.invoke(Unknown Source)
    	... 34 more

Pelo StackTrace, não há problema com seu where e sim com a implementação do método salvar, onde você está tentando acessar invocar método de um objeto null.
Imagino que seja o pedidoCompraBean ou o getUltimoPedido() que estejam null.