Bugbear: Add Mutable Parameter fixes (#9682)

Part of #9366

Adds in fixes for B006 and B008, both relating to mutable parameter lint errors.

Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>

1 files changed, 3 insertions, 1 deletions

diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py

index 9701b76d0f..3b6660c873 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -169,7 +169,7 @@ class RegistrationHandler(BaseHandler):
         user_type: Optional[str] = None,
         default_display_name: Optional[str] = None,
         address: Optional[str] = None,
-        bind_emails: Iterable[str] = [],
+        bind_emails: Optional[Iterable[str]] = None,
         by_admin: bool = False,
         user_agent_ips: Optional[List[Tuple[str, str]]] = None,
         auth_provider_id: Optional[str] = None,
@@ -204,6 +204,8 @@ class RegistrationHandler(BaseHandler):
         Raises:
             SynapseError if there was a problem registering.
         """
+        bind_emails = bind_emails or []
+
         await self.check_registration_ratelimit(address)
 
         result = await self.spam_checker.check_registration_for_spam(