printer yin BUGFIX keyless list print

Fixes #1802
diff --git a/src/printer_yin.c b/src/printer_yin.c
index 9739ede..0c4bc22 100644
--- a/src/printer_yin.c
+++ b/src/printer_yin.c
@@ -881,7 +881,7 @@
         ypr_substmt(pctx, LY_STMT_UNIQUE, u, list->uniques[u].str, list->exts);
     }
 
-    ypr_config(pctx, node->flags, node->exts, NULL);
+    ypr_config(pctx, node->flags, node->exts, &flag);
 
     if (list->flags & LYS_SET_MIN) {
         ypr_unsigned(pctx, LY_STMT_MIN_ELEMENTS, 0, list->exts, list->min);