CloudPickle returns IndexError when trying to pickle _UnPicklable object

The error happens at https://github.com/cloudpipe/cloudpickle/blob/a76f0812ccdbbd1397f36d536dc4d57b6d0557d6/cloudpickle/cloudpickle_fast.py#L634.

When I try to pickle the below class, it is failing with `NotImplementedError` then it calls the exception, since `NotImplemented` error is a subclass of `RuntimeError`, the above code fails during `except` since `e.args` is empty.

```
with io.BytesIO() as file:
pickler = cloudpickle.CloudPickler(file)
pickler.dump(_Unpicklable(1))

class _Unpicklable(object):
def __init__(self, value):
self.value = value

def __eq__(self, other):
return self.value == other.value

def __getstate__(self):
raise NotImplementedError()

def __setstate__(self, state):
raise NotImplementedError()
```