Qtconsole crash when closing with Ctrl-d and c.IPythonQtConsoleApp.maximize option set to True

[PhML]

If I use a profile with c.IPythonQtConsoleApp.maximize = True and try to exit qtconsole using Ctrl-d, after confirm I want to close all, I get this:

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/IPython/qt/base_frontend_mixin.py", line 138, in _dispatch
    handler(msg)
  File "/usr/lib/python2.7/site-packages/IPython/qt/console/ipython_widget.py", line 186, in _handle_execute_reply
    super(IPythonWidget, self)._handle_execute_reply(msg)
  File "/usr/lib/python2.7/site-packages/IPython/qt/console/frontend_widget.py", line 425, in _handle_execute_reply
    self.kernel_client.iopub_channel.flush()
  File "/usr/lib/python2.7/site-packages/IPython/qt/kernel_mixins.py", line 127, in flush
    super(QtIOPubChannelMixin, self).flush()
  File "/usr/lib/python2.7/site-packages/IPython/kernel/channels.py", line 448, in flush
    self.ioloop.add_callback(self._flush)
  File "/usr/lib/python2.7/site-packages/tornado/ioloop.py", line 732, in add_callback
    raise RuntimeError("IOLoop is closing")
RuntimeError: IOLoop is closing```

[minrk]

This is fixed in master.