vl.c: select_machine(): use ERRP_GUARD instead of error propagation

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/system/vl.c b/system/vl.c
index 4dc8626..fda93d1 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -1665,28 +1665,28 @@
 
 static MachineClass *select_machine(QDict *qdict, Error **errp)
 {
+    ERRP_GUARD();
     const char *machine_type = qdict_get_try_str(qdict, "type");
     GSList *machines = object_class_get_list(TYPE_MACHINE, false);
-    MachineClass *machine_class;
-    Error *local_err = NULL;
+    MachineClass *machine_class = NULL;
 
     if (machine_type) {
         machine_class = find_machine(machine_type, machines);
         qdict_del(qdict, "type");
         if (!machine_class) {
-            error_setg(&local_err, "unsupported machine type");
+            error_setg(errp, "unsupported machine type");
         }
     } else {
         machine_class = find_default_machine(machines);
         if (!machine_class) {
-            error_setg(&local_err, "No machine specified, and there is no default");
+            error_setg(errp, "No machine specified, and there is no default");
         }
     }
 
     g_slist_free(machines);
-    if (local_err) {
-        error_append_hint(&local_err, "Use -machine help to list supported machines\n");
-        error_propagate(errp, local_err);
+    if (!machine_class) {
+        error_append_hint(errp,
+                          "Use -machine help to list supported machines\n");
     }
     return machine_class;
 }