Suddenly throw an exeception:

14:45:15.171 [ERROR] [msgbrdmgr] Uncaught exception escaped
com.google.gwt.dev.shell.HostedModeException: Something other than a boolean was returned from JSNI method '@com.extjs.gxt.ui.client.core.DomQuery::is(Lcom/google/gwt/user/client/Element;Ljava/lang/String': JS value of type undefined, expected boolean
at com.google.gwt.dev.shell.JsValueGlue.get(JsValueGlue.java:100)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeBoolean(ModuleSpace.java:186)
at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeBoolean(JavaScriptHost.java:35)
at com.extjs.gxt.ui.client.core.DomQuery.is(DomQuery.java)
at com.extjs.gxt.ui.client.core.El.findParentElement(El.java:703)
at com.extjs.gxt.ui.client.widget.grid.GridView.findRow(GridView.java:282)
at com.extjs.gxt.ui.client.widget.grid.GridView.findRowIndex(GridView.java:292)
at com.extjs.gxt.ui.client.event.GridEvent.getRowIndex(GridEvent.java:115)
at com.extjs.gxt.ui.client.widget.grid.GridView.handleComponentEvent(GridView.java:1165)
at com.extjs.gxt.ui.client.widget.grid.Grid.onComponentEvent(Grid.java:514)
at com.extjs.gxt.ui.client.widget.Component.onBrowserEvent(Component.java:884)
at com.google.gwt.user.client.DOM.dispatchEventImpl(DOM.java:1310)
at com.google.gwt.user.client.DOM.dispatchEvent(DOM.java:1266)
at sun.reflect.GeneratedMethodAccessor293.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:326)
at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:207)
at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:129)
at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:561)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)
at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:214)
at sun.reflect.GeneratedMethodAccessor287.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:281)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:531)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:352)
at java.lang.Thread.run(Thread.java:662)