journal: use empty_to_null() in one more place

Follow-up for 45bcab66a9c23a74107118d310e09a46f28494fd.

diff --git a/src/journal/cat.c b/src/journal/cat.c
index 1634f30b44e1958940ed364f31384ba354624397..90d4f5352fd4973424a2918caef1b0faec65dde3 100644 (file)
--- a/src/journal/cat.c
+++ b/src/journal/cat.c
@@ -95,10 +95,7 @@ static int parse_argv(int argc, char *argv[]) {
                         return version();
 
                 case 't':
-                        if (isempty(optarg))
-                                arg_identifier = NULL;
-                        else
-                                arg_identifier = optarg;
+                        arg_identifier = empty_to_null(optarg);
                         break;
 
                 case 'p':
@@ -122,10 +119,7 @@ static int parse_argv(int argc, char *argv[]) {
                         break;
 
                 case ARG_NAMESPACE:
-                        if (isempty(optarg))
-                                arg_namespace = NULL;
-                        else
-                                arg_namespace = optarg;
+                        arg_namespace = empty_to_null(optarg);
                         break;
 
                 case '?':