data tree BUGFIX unitialized value
diff --git a/src/tree_data.c b/src/tree_data.c
index a3db3ba..c02dfcb 100644
--- a/src/tree_data.c
+++ b/src/tree_data.c
@@ -4107,6 +4107,7 @@
 
     LY_CHECK_ARG_RET(NULL, ctx_node, xpath, set, LY_EINVAL);
 
+    *set = NULL;
     memset(&xp_set, 0, sizeof xp_set);
 
     /* compile expression */