init: change exec parsing to make SECLABEL optional

Allow SECLABEL to be - to denote default

Change-Id: I58cdc6c805dc6e50dc42b7e13e72d0eaf4864f11
diff --git a/init/init.cpp b/init/init.cpp
index 60fcf64..2500985 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -380,7 +380,8 @@
 
     if ((svc->flags & SVC_EXEC) != 0) {
         INFO("SVC_EXEC pid %d (uid %d gid %d+%zu context %s) started; waiting...\n",
-             svc->pid, svc->uid, svc->gid, svc->nr_supp_gids, svc->seclabel);
+             svc->pid, svc->uid, svc->gid, svc->nr_supp_gids,
+             svc->seclabel ? : "default");
         waiting_for_exec = true;
     }