Table formatter doesn't support empty list

[Cedric Brandily]

Table formatter is not able to handle empty list (other formatters support it) in cliff 1.17.0 because it tries to visit the first element of an empty list.

Typical example with neutronclient:

neutron port-list --json
[]

neutron --debug port-list
Traceback (most recent call last):
  File "/home/T0102996/projects/os/neutronclient/neutronclient/shell.py", line 826, in run_subcommand
    return run_command(cmd, cmd_parser, sub_argv)
  File "/home/T0102996/projects/os/neutronclient/neutronclient/shell.py", line 106, in run_command
    return cmd.run(known_args)
  File "/home/T0102996/projects/os/neutronclient/.tox/py27/local/lib/python2.7/site-packages/cliff/display.py", line 88, in run
    self.produce_output(parsed_args, column_names, data)
  File "/home/T0102996/projects/os/neutronclient/.tox/py27/local/lib/python2.7/site-packages/cliff/lister.py", line 51, in produce_output
    parsed_args,
  File "/home/T0102996/projects/os/neutronclient/.tox/py27/local/lib/python2.7/site-packages/cliff/formatters/table.py", line 64, in emit_list
    stdout, x, int(parsed_args.max_width), min_width)
  File "/home/T0102996/projects/os/neutronclient/.tox/py27/local/lib/python2.7/site-packages/cliff/formatters/table.py", line 148, in _assign_max_widths
    first_line = x.get_string().splitlines()[0]
IndexError: list index out of range
list index out of range

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/280982

[OpenStack Infra (hudson-openstack)]

Change abandoned by Cedric Brandily (<email address hidden>) on branch: master
Review: https://review.openstack.org/280982