steps to reproduce

1. run the code below

   <if test="${notExistingVar}">
       <label value="Label Text"/>
   </if>
   

actual result

java.lang.NullPointerException
at org.zkoss.zuti.zul.If$1.setValue(If.java:57)
at org.zkoss.zuti.zul.If$1.setValue(If.java:55)
at org.zkoss.zk.ui.metainfo.Property.assign0(Property.java:203)
at org.zkoss.zk.ui.metainfo.Property.assign(Property.java:171)
at org.zkoss.zk.ui.metainfo.ShadowInfo.apply(ShadowInfo.java:112)
at org.zkoss.zk.ui.impl.UiEngineImpl.execCreateChild(UiEngineImpl.java:835)
at org.zkoss.zk.ui.impl.UiEngineImpl.execCreate0(UiEngineImpl.java:807)
at org.zkoss.zk.ui.impl.UiEngineImpl.execCreate(UiEngineImpl.java:709)
at org.zkoss.zk.ui.impl.UiEngineImpl.execCreateChild0(UiEngineImpl.java:923)
at org.zkoss.zk.ui.impl.UiEngineImpl.execCreateChild(UiEngineImpl.java:877)
at org.zkoss.zk.ui.impl.UiEngineImpl.execCreate0(UiEngineImpl.java:748)
at org.zkoss.zk.ui.impl.UiEngineImpl.execCreateChild(UiEngineImpl.java:822)
at org.zkoss.zk.ui.impl.UiEngineImpl.execCreate0(UiEngineImpl.java:771)
at org.zkoss.zk.ui.impl.UiEngineImpl.execCreate(UiEngineImpl.java:709)
at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage0(UiEngineImpl.java:452)
at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage(UiEngineImpl.java:358)
at org.zkoss.zk.ui.http.DHtmlLayoutServlet.process(DHtmlLayoutServlet.java:217)

workaround

• <if test="${notExistingVar eq null}">