Index: Slim/Player/Sync.pm
===================================================================
--- Slim/Player/Sync.pm	(revision 3144)
+++ Slim/Player/Sync.pm	(working copy)
@@ -385,6 +385,7 @@
 
 sub masterOrSelf {
 	my $client = shift;
+	assert($client);
 	return $client->master || $client;
 }