bluesky: app.bsky.graph.getFollowers, handle no user

tests/test_xrpc_graph.py

@@ -45,6 +45,10 @@ OTHER_FOLLOW_AS2['actor'].update({
 @patch('requests.get')
 class XrpcGraphTest(testutil.TestCase):
 
+    def test_getProfile_no_user(self, _):
+        resp = self.client.get('/xrpc/app.bsky.graph.getFollowers')
+        self.assertEqual(400, resp.status_code)
+
     def test_getFollowers_not_domain(self, mock_get):
         resp = self.client.get('/xrpc/app.bsky.graph.getFollowers',
                               query_string={'user': 'not a domain'})

xrpc_graph.py

@@ -22,7 +22,7 @@ def get_followers(query_prop, output_field, user=None, limit=50, before=None):
       dict, XRPC method output
     """
     # TODO: what is user?
-    if not re.match(util.DOMAIN_RE, user):
+    if not user or not re.match(util.DOMAIN_RE, user):
         raise ValueError(f'{user} is not a domain')
 
     followers = []