Avoid an extra operation

In the catalog code, tsan also complained of testing
the variable without locking and that was done a few lines below
diff --git a/catalog.c b/catalog.c
index f33a0aa..fb586c1 100644
--- a/catalog.c
+++ b/catalog.c
@@ -1407,8 +1407,6 @@
 	return(-1);
     if (catal->URL == NULL)
 	return(-1);
-    if (catal->children != NULL)
-	return(-1);
 
     /*
      * lock the whole catalog for modification