Add an empty profile for anonymous users

It evaluates to `None`, but at least it doesn’t raise an `AttributeError` now.

calsocial/security.py

@@ -35,6 +35,15 @@ class AnonymousUser(BaseAnonymousUser):
 
         return current_app.timezone
 
+    @property
+    def profile(self):
+        """The profile of the anonymous user
+
+        Always evaluates to ``None``
+        """
+
+        return None
+
 
 @user_logged_in.connect
 def login_handler(app, user):  # pylint: disable=unused-argument