Revert "AAAA filter: Reject instead of sending an empty response"

This reverts commit aceb8b3.

Author: jedisct1

dnscrypt-proxy/plugin_block_ipv6.go

@@ -33,6 +33,11 @@ func (plugin *PluginBlockIPv6) Eval(pluginsState *PluginsState, msg *dns.Msg) er
 	if question.Qclass != dns.ClassINET || question.Qtype != dns.TypeAAAA {
 		return nil
 	}
-	pluginsState.action = PluginsActionReject
+	synth, err := EmptyResponseFromMessage(msg)
+	if err != nil {
+		return err
+	}
+	pluginsState.synthResponse = synth
+	pluginsState.action = PluginsActionSynth
 	return nil
 }