validation BUGFIX mandatory nodes with when

Validation can be generated only if all the
node's when are true, it is disabled otherwise.
diff --git a/src/tree_data.c b/src/tree_data.c
index a1acddc..91d69a9 100644
--- a/src/tree_data.c
+++ b/src/tree_data.c
@@ -356,7 +356,7 @@
             LY_CHECK_GOTO(ret, cleanup);
 
             /* perform final validation that assumes the data tree is final */
-            LY_CHECK_GOTO(ret = lyd_validate_final_r(*first2, NULL, mod, validate_options, 0), cleanup);
+            LY_CHECK_GOTO(ret = lyd_validate_final_r(*first2, NULL, NULL, mod, validate_options, 0), cleanup);
         }
     }