title: GWT app throws exception when client in debug mode
body: <p>If I launch the URL [code]http://localhost:8888/app1.html?[/code] and click a button it works fine. Calls into my RPC on localhost fine.  However if I then change the URL so the client is in debug mode ie 
  [code]http://localhost:8888/app1.html?gwt.codesvr=localhost:[/code]it then throws an exception at the point where it calls into the RPC service on my local server.</p>
  
  <p>Here is the exception code.</p>
  
  
  
  <pre class="lang-java prettyprint-override"><code>08:08:41.482 [ERROR] [nquizitive] Uncaught exception escaped
  
  com.google.gwt.event.shared.UmbrellaException: One or more exceptions caught, see full set in UmbrellaException#getCauses
      at com.google.gwt.event.shared.HandlerManager.fireEvent(HandlerManager.java:129)
      at com.google.gwt.user.client.ui.Widget.fireEvent(Widget.java:129)
      at com.google.gwt.event.dom.client.DomEvent.fireNativeEvent(DomEvent.java:116)
      at com.google.gwt.user.client.ui.Widget.onBrowserEvent(Widget.java:177)
      at com.google.gwt.user.client.DOM.dispatchEventImpl(DOM.java:1351)
      at com.google.gwt.user.client.DOM.dispatchEvent(DOM.java:1307)
      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 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:172)
      at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:337)
      at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:218)
      at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
      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:213)
      at sun.reflect.GeneratedMethodAccessor31.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      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:172)
      at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:292)
      at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:546)
      at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
      at java.lang.Thread.run(Unknown Source)
  Caused by: java.lang.AssertionError: null
      at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.&amp;lt;init&amp;gt;(RequestCallbackAdapter.java:182)
      at com.google.gwt.user.client.rpc.impl.RemoteServiceProxy.doCreateRequestCallback(RemoteServiceProxy.java:347)
      at com.google.gwt.user.client.rpc.impl.RemoteServiceProxy.doPrepareRequestBuilderImpl(RemoteServiceProxy.java:433)
      at com.google.gwt.user.client.rpc.impl.RemoteServiceProxy.doInvoke(RemoteServiceProxy.java:368)
      at com.google.gwt.user.client.rpc.impl.RemoteServiceProxy$ServiceHelper.finish(RemoteServiceProxy.java:74)
      at com.app.nquizitive.client.service.CategoryService_Proxy.createCategory(CategoryService_Proxy.java:32)
      at com.app.nquizitive.client.presenter.HomeViewPresenter$2.onClick(HomeViewPresenter.java:60)
      at com.google.gwt.event.dom.client.ClickEvent.dispatch(ClickEvent.java:54)
      at com.google.gwt.event.dom.client.ClickEvent.dispatch(ClickEvent.java:1)
      at com.google.gwt.event.shared.GwtEvent.dispatch(GwtEvent.java:1)
      at com.google.web.bindery.event.shared.EventBus.dispatchEvent(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.HandlerManager.fireEvent(HandlerManager.java:127)
      at com.google.gwt.user.client.ui.Widget.fireEvent(Widget.java:129)
      at com.google.gwt.event.dom.client.DomEvent.fireNativeEvent(DomEvent.java:116)
      at com.google.gwt.user.client.ui.Widget.onBrowserEvent(Widget.java:177)
      at com.google.gwt.user.client.DOM.dispatchEventImpl(DOM.java:1351)
      at com.google.gwt.user.client.DOM.dispatchEvent(DOM.java:1307)
      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 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:172)
      at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:337)
      at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:218)
      at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
      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:213)
      at sun.reflect.GeneratedMethodAccessor31.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      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:172)
      at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:292)
      at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:546)
      at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
      at java.lang.Thread.run(Unknown Source)
  </code></pre>
  
  <p>The line that causes the issue is the callinto the category service.</p>
  
  <pre class="lang-java prettyprint-override"><code>public void onClick(ClickEvent event){
      display.getNewCategoryName();
      categoryService.createCategory( display.getNewCategoryName(), null )
  }
  </code></pre>
  
  <p>Just noticed that I get the exception because the Async callback is null.  Can I not set it to null if i am not interested in the response.  This is basically a fire and forget call.</p>
  
  <p>Here is the code that works</p>
  
  <pre class="lang-java prettyprint-override"><code>public void onClick(ClickEvent event){
  
       display.getNewCategoryName();
       categoryService.createCategory( display.getNewCategoryName(), new AsyncCallback(){
  
           public void onFailure(Throwable caught){
               Window.alert("Error fetching categorys");
           }
  
           @Override
           public void onSuccess(Object result){
               //New Category added so update display
               fetchCategorys();
           }
  
       });
  }
  </code></pre>
  
  <p>Still don't understand why a null Async callback object works in run mode :(</p>