When you click on a message that is an ObjectMessage type, but no payload has been set, the DefaultMessageRenderer throws a NullPointerException.

I think it would be more intuitive if the renderer returned a simple message saying that the payload was empty.

Unable to display message:
java.lang.NullPointerException
at hermes.renderers.DefaultMessageRenderer.handleObjectMessage(DefaultMessageRenderer.java:349)
at hermes.renderers.DefaultMessageRenderer.render(DefaultMessageRenderer.java:517)
at hermes.browser.components.MessagePayloadPanel.setMessage(MessagePayloadPanel.java:90)
at hermes.browser.actions.BrowserAction.valueChanged(BrowserAction.java:898)
at hermes.browser.actions.BrowserAction$2.run(BrowserAction.java:576)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)