Fix that sending server notices fail if avatar is `None` (#13566)

Indroduced in #11846.

1 files changed, 1 insertions, 1 deletions

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

index d1909665d6..65b9a655d4 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -689,7 +689,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                 errcode=Codes.BAD_JSON,
             )
 
-        if "avatar_url" in content:
+        if "avatar_url" in content and content.get("avatar_url") is not None:
             if not await self.profile_handler.check_avatar_size_and_mime_type(
                 content["avatar_url"],
             ):