When executing `dvc import-url remote://some-webdav/data`, the name of
the WebDAV dependency in the created stage for data used to be `None`.
This resulted in the following error:
```
Traceback (most recent call last):
File "/home/schubert/projects/dvc/dvc/main.py", line 76, in main
ret = cmd.run()
File "/home/schubert/projects/dvc/dvc/command/imp_url.py", line 14, in run
self.repo.imp_url(
File "/home/schubert/projects/dvc/dvc/repo/__init__.py", line 51, in wrapper
return f(repo, *args, **kwargs)
File "/home/schubert/projects/dvc/dvc/repo/scm_context.py", line 4, in run
result = method(repo, *args, **kw)
File "/home/schubert/projects/dvc/dvc/repo/imp_url.py", line 54, in imp_url
stage.run()
File "/home/schubert/miniconda3/tmp/envs/some-project/lib/python3.8/site-packages/funcy/decorators.py", line 39, in wrapper
return deco(call, *dargs, **dkwargs)
File "/home/schubert/projects/dvc/dvc/stage/decorators.py", line 36, in rwlocked
return call()
File "/home/schubert/miniconda3/tmp/envs/some-project/lib/python3.8/site-packages/funcy/decorators.py", line 60, in __call__
return self._func(*self._args, **self._kwargs)
File "/home/schubert/projects/dvc/dvc/stage/__init__.py", line 450, in run
self.save()
File "/home/schubert/projects/dvc/dvc/stage/__init__.py", line 395, in save
self.md5 = self.compute_md5()
File "/home/schubert/projects/dvc/dvc/stage/__init__.py", line 388, in compute_md5
m = compute_md5(self)
File "/home/schubert/projects/dvc/dvc/stage/utils.py", line 167, in compute_md5
return dict_md5(
File "/home/schubert/projects/dvc/dvc/utils/__init__.py", line 118, in dict_md5
return dict_hash(d, "md5", **kwargs)
File "/home/schubert/projects/dvc/dvc/utils/__init__.py", line 113, in dict_hash
byts = json.dumps(filtered, sort_keys=True).encode("utf-8")
File "/home/schubert/miniconda3/tmp/envs/some-project/lib/python3.8/json/__init__.py", line 234, in dumps
return cls(
File "/home/schubert/miniconda3/tmp/envs/some-project/lib/python3.8/json/encoder.py", line 199, in encode
chunks = self.iterencode(o, _one_shot=True)
File "/home/schubert/miniconda3/tmp/envs/some-project/lib/python3.8/json/encoder.py", line 257, in iterencode
return _iterencode(o, 0)
TypeError: '<' not supported between instances of 'str' and 'NoneType'
```
Frederik Schubert