policies/reputation: only change score when credentials contain username

passbook/policies/reputation/signals.py

@@ -32,6 +32,7 @@ def update_score(request: HttpRequest, username: str, amount: int):
 # pylint: disable=unused-argument
 def handle_failed_login(sender, request, credentials, **_):
     """Lower Score for failed loging attempts"""
+    if "username" in credentials:
         update_score(request, credentials.get("username"), -1)