Unable to add record to Grouped listgrid

I can add new records to a listgrid (via listGrid.getDataAsRecordList().add(newRecord)) without issue.

When I change the listGrid to group on a column (with/without overriding getGroupValue()) I get the warning: Tree.add(): specified parent node:undef is not in the tree, returning
followed by a stackTrace, below.

SmartGWT version: SmartGWT 4.0p

This happens in any browser

StackTrace in Eclipse development console:

13:51:07.935 [ERROR] [webportal] 13:51:07.535:WARN:Log:Tree.add(): specified parent node:undef is not in the tree, returning

com.smartgwt.client.core.JsObject$SGWT_WARN: 13:51:07.535:WARN:Log:Tree.add(): specified parent node:undef is not in the tree, returning
at sun.reflect.GeneratedConstructorAccessor33.newInst ance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newI nstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Construc tor.java:526)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(Meth odAdaptor.java:105)
at com.google.gwt.dev.shell.MethodDispatch.invoke(Met hodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invok e(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reac tToMessagesWhileWaitingForReturn(BrowserChannelSer ver.java:338)
at com.google.gwt.dev.shell.BrowserChannelServer.invo keJavascript(BrowserChannelServer.java:219)
at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke (ModuleSpaceOOPHM.java:136)
at com.google.gwt.dev.shell.ModuleSpace.invokeNative( ModuleSpace.java:571)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeV oid(ModuleSpace.java:299)
at com.google.gwt.dev.shell.JavaScriptHost.invokeNati veVoid(JavaScriptHost.java:107)
at com.smartgwt.client.data.RecordList.add(RecordList .java)
at com.atm.webportal.client.presenter.TargetsPanelPre senter.addTargetsToPanel(TargetsPanelPresenter.jav a:145)
at com.atm.webportal.client.ContentContainer$10.onTar getsReceived(ContentContainer.java:385)
at com.atm.webportal.client.event.TargetsReceivedEven t.dispatch(TargetsReceivedEvent.java:24)
at com.atm.webportal.client.event.TargetsReceivedEven t.dispatch(TargetsReceivedEvent.java:1)
at com.google.gwt.event.shared.GwtEvent.dispatch(GwtE vent.java:1)
at com.google.web.bindery.event.shared.EventBus.dispa tchEvent(EventBus.java:40)
at com.google.web.bindery.event.shared.SimpleEventBus .doFire(SimpleEventBus.java:193)
at com.google.web.bindery.event.shared.SimpleEventBus .fireEvent(SimpleEventBus.java:88)
at com.google.gwt.event.shared.SimpleEventBus.fireEve nt(SimpleEventBus.java:52)
at com.google.gwt.event.shared.EventBus.castFireEvent (EventBus.java:67)
at com.google.gwt.event.shared.SimpleEventBus.fireEve nt(SimpleEventBus.java:57)
at com.atm.webportal.client.WebPortal.readTargets(Web Portal.java:479)
at com.atm.webportal.client.WebPortal.handleMessage(W ebPortal.java:460)
at com.atm.webportal.client.WebPortal.access$1(WebPor tal.java:457)
at com.atm.webportal.client.WebPortal$3$1.onMessage(W ebPortal.java:306)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Native MethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(De legatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(Meth odAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(Met hodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invok e(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reac tToMessages(BrowserChannelServer.java:293)
at com.google.gwt.dev.shell.BrowserChannelServer.proc essConnection(BrowserChannelServer.java:547)
at com.google.gwt.dev.shell.BrowserChannelServer.run( BrowserChannelServer.java:364)
at java.lang.Thread.run(Thread.java:724)