xpath FEATURE ignore when state for lyd_find_xpath

New flag defined for the purpose.
diff --git a/src/tree_data.c b/src/tree_data.c
index 5d6c63c..2706378 100644
--- a/src/tree_data.c
+++ b/src/tree_data.c
@@ -3344,7 +3344,7 @@
     LY_CHECK_GOTO(ret, cleanup);
 
     /* evaluate expression */
-    ret = lyxp_eval(exp, NULL, LY_PREF_JSON, NULL, ctx_node, ctx_node, &xp_set, 0);
+    ret = lyxp_eval(exp, NULL, LY_PREF_JSON, NULL, ctx_node, ctx_node, &xp_set, LYXP_IGNORE_WHEN);
     LY_CHECK_GOTO(ret, cleanup);
 
     /* allocate return set */