lnrpc/watchtowerrpc: prevent watchtowerrpc panic when tower not active

subrpcserver_config.go

@@ -216,6 +216,9 @@ func (s *subRPCServerConfigs) PopulateDependencies(cc *chainControl,
 		case *watchtowerrpc.Config:
 			subCfgValue := extractReflectValue(subCfg)
 
+			subCfgValue.FieldByName("Active").Set(
+				reflect.ValueOf(tower != nil),
+			)
 			subCfgValue.FieldByName("Tower").Set(
 				reflect.ValueOf(tower),
 			)