get_params is now ignored if not set

[joker234]

When the last example from the readme is tried, this error occurs.

client = ors.Client(base_url=host)
resp = client.request(
    url=f'/v2/directions/{profile}/{format}',
    post_json={
        'coordinates': coords
    })

Error:

  …
  File "$HOME/.local/lib/python3.8/site-packages/openrouteservice/client.py", line 163, in request
    authed_url = self._generate_auth_url(url,
  File "$HOME/.local/lib/python3.8/site-packages/openrouteservice/client.py", line 267, in _generate_auth_url
    return path + "?" + _urlencode_params(params)
  File "$HOME/.local/lib/python3.8/site-packages/openrouteservice/client.py", line 330, in _urlencode_params
    params = [(key, _normalize_for_urlencode(val)) for key, val in params]
TypeError: 'NoneType' object is not iterable

If the parameter get_params={} is added, everything works as expected. The fix in this PR skips the urlencode line and just returns the path when the params are none. A test is added as well.

[coveralls]

Pull Request Test Coverage Report for Build 134

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+1.3%) to 95.247%

---

Totals
Change from base Build 131:	1.3%
Covered Lines:	521
Relevant Lines:	547

---

💛 - Coveralls

[joker234]

Alternatives would be to

1. change the readme example, or
2. catch the error in:

   openrouteservice-py/openrouteservice/client.py

   Lines 320 to 334 in 7615c33

   	def _urlencode_params(params):
   	"""URL encodes the parameters.
   	:param params: The parameters
   	:type params: list of key/value tuples.
   	:rtype: string
   	"""
   	# urlencode does not handle unicode strings in Python 2.
   	# Firstly, normalize the values so they get encoded correctly.
   	params = [(key, _normalize_for_urlencode(val)) for key, val in params]
   	# Secondly, unquote unreserved chars which are incorrectly quoted
   	# by urllib.urlencode, causing invalid auth signatures. See GH #72
   	# for more info.
   	return requests.utils.unquote_unreserved(urlencode(params))

[nilsnolde]

I'll just merge now, hope someone of the team will soon (at least eventually..) maintain this..