Error when starting ZT - No attribute 'update_pipe'.

[sumanthvrao]

Sometimes on startup of ZT, an exception with the following traceback:

Loading -Exception in thread Thread-5:
Traceback (most recent call last):
  File "/home/sumanthvrao/.pyenv/versions/3.6.5/lib/python3.6/threading.py", line 916, in _bootstrap_inner
    self.run()
  File "/home/sumanthvrao/.pyenv/versions/3.6.5/lib/python3.6/threading.py", line 864, in run
    self._target(*self._args, **self._kwargs)
  File "/home/sumanthvrao/Git_Hub/zulip-terminal/zulipterminal/ui_tools/views.py", line 440, in update_user_list
    self.view.controller.update_screen()
  File "/home/sumanthvrao/Git_Hub/zulip-terminal/zulipterminal/core.py", line 81, in update_screen
    os.write(self.update_pipe, b'1')
AttributeError: 'Controller' object has no attribute 'update_pipe'

This indicates that there is most likely a race condition occurring during startup.