Fix bug when federation_domain_whitelist is an emtpy list

Outbound federation were incorrectly allowed when the config option was
set to an empty list

1 files changed, 1 insertions, 1 deletions

diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py

index 44b61e70a4..b34bb8e31a 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -133,7 +133,7 @@ class MatrixFederationHttpClient(object):
                 failures, connection failures, SSL failures.)
         """
         if (
-            self.hs.config.federation_domain_whitelist and
+            self.hs.config.federation_domain_whitelist is not None and
             destination not in self.hs.config.federation_domain_whitelist
         ):
             raise FederationDeniedError(destination)