Fix ConcurrentModificationException in ControlSequenceVisualizer

Stack was : 

Exception in thread "AWT-EventQueue-0" java.util.ConcurrentModificationException
	at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
	at java.util.AbstractList$Itr.next(AbstractList.java:343)
	at com.jediterm.terminal.debug.ControlSequenceVisualizer.writeChunksToFile(ControlSequenceVisualizer.java:54)
	at com.jediterm.terminal.debug.ControlSequenceVisualizer.getVisualizedString(ControlSequenceVisualizer.java:30)
	at com.jediterm.terminal.debug.DebugBufferType$6.getValue(DebugBufferType.java:41)
	at com.jediterm.terminal.ui.JediTermWidget.getBufferText(JediTermWidget.java:133)
	at com.jediterm.terminal.debug.BufferPanel$1Updater.update(BufferPanel.java:37)
	at com.jediterm.terminal.debug.BufferPanel$1Updater.actionPerformed(BufferPanel.java:45)
	at javax.swing.Timer.fireActionPerformed(Timer.java:291)
	at javax.swing.Timer$DoPostEvent.run(Timer.java:221)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:641)
	at java.awt.EventQueue.access$000(EventQueue.java:84)
	at java.awt.EventQueue$1.run(EventQueue.java:602)
	at java.awt.EventQueue$1.run(EventQueue.java:600)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:611)
	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)