[Bug] client.node.list filters by default on offline nodes
**Describe the bug**
`client.node.list` filters on offline nodes by default. It should not filter on the _status_ field at all.

**To Reproduce**
```
>>> client.node.list()
Making request: GET | http://127.0.0.1:5000/node | {'page': 1, 'per_page': 20, 'include': ['metadata'], 'name': None, 'organization_id': None, 'collaboration_id': None, 'ip': None, 'status': 'offline', 'last_seen_from': None, 'last_seen_till': None}
{'data': [], 'links': {'first': '/node?page=1&per_page=20&include=metadata&status=offline', 'self': '/node?page=1&per_page=20&include=metadata&status=offline'}}
```
diff --git a/vantage6-client/vantage6/client/__init__.py b/vantage6-client/vantage6/client/__init__.py
index 46bd8e3e..0f96d7f9 100644
--- a/vantage6-client/vantage6/client/__init__.py
+++ b/vantage6-client/vantage6/client/__init__.py
@@ -941,10 +941,11 @@ class UserClient(ClientBase):
                 'page': page, 'per_page': per_page, 'include': includes,
                 'name': name, 'organization_id': organization,
                 'collaboration_id': collaboration, 'ip': ip,
-                'status': 'online' if is_online else 'offline',
                 'last_seen_from': last_seen_from,
                 'last_seen_till': last_seen_till
             }
+            if is_online is not None:
+                params['status'] = 'online' if is_online else 'offline'
             return self.parent.request('node', params=params)
 
         @post_filtering(iterable=False)
['vantage6-client/vantage6/client/__init__.py']