ErrorTable isn't thread safe

java.lang.NullPointerException javax.swing.DefaultRowSorter.convertRowIndexToModel(DefaultRowSorter.java:501) javax.swing.JTable.convertRowIndexToModel(JTable.java:2611) javax.swing.JTable.convertRowIndexToModel(JTable.java:4335) javax.swing.JTable.convertSelectionToModel(JTable.java:4318) javax.swing.JTable.access$300(JTable.java:199) javax.swing.JTable$SortManager.cacheModelSelection(JTable.java:3953) javax.swing.JTable$SortManager.cacheSelection(JTable.java:3948) javax.swing.JTable$SortManager.prepareForChange(JTable.java:3887) javax.swing.JTable.sortedTableChanged(JTable.java:4100) javax.swing.JTable.tableChanged(JTable.java:4383) javax.swing.table.AbstractTableModel.fireTableChanged(AbstractTableModel.java:280) javax.swing.table.AbstractTableModel.fireTableRowsUpdated(AbstractTableModel.java:230) com.dmdirc.addons.ui_swing.dialogs.error.ErrorTableModel$3.run(ErrorTableModel.java:290) java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) java.awt.EventQueue.dispatchEvent(EventQueue.java:633) com.dmdirc.addons.ui_swing.DMDircEventQueue.dispatchEvent(DMDircEventQueue.java:79) java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296) java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211) java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201) java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196) java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188) java.awt.EventDispatchThread.run(EventDispatchThread.java:122)