Preferences categories are missing icons

java.lang.NullPointerException java.lang.NullPointerException com.dmdirc.ui.IconManager.getIconURL(IconManager.java:165) com.dmdirc.ui.IconManager.getIcon(IconManager.java:90) com.dmdirc.addons.ui_swing.dialogs.prefs.IconLoader.doInBackground(IconLoader.java:59) com.dmdirc.addons.ui_swing.dialogs.prefs.IconLoader.doInBackground(IconLoader.java:35) javax.swing.SwingWorker$1.call(SwingWorker.java:277) java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) java.util.concurrent.FutureTask.run(FutureTask.java:138) javax.swing.SwingWorker.run(SwingWorker.java:316) java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) java.lang.Thread.run(Thread.java:662) Which caused: java.util.concurrent.ExecutionException: java.lang.NullPointerException java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:222) java.util.concurrent.FutureTask.get(FutureTask.java:83) javax.swing.SwingWorker.get(SwingWorker.java:582) com.dmdirc.addons.ui_swing.dialogs.prefs.IconLoader.done(IconLoader.java:66) javax.swing.SwingWorker$5.run(SwingWorker.java:717) javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(SwingWorker.java:814) sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:95) javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(SwingWorker.java:824) javax.swing.Timer.fireActionPerformed(Timer.java:271) javax.swing.Timer$DoPostEvent.run(Timer.java:201) java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) java.awt.EventQueue.dispatchEvent(EventQueue.java:597) com.dmdirc.addons.ui_swing.DMDircEventQueue.dispatchEvent(DMDircEventQueue.java:69) java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) java.awt.EventDispatchThread.run(EventDispatchThread.java:122)