libyang MAINTENANCE fox uninitialized vars warnings

Even though they all are false-positives.
diff --git a/src/tree_data_free.c b/src/tree_data_free.c
index e4da1b3..42db31c 100644
--- a/src/tree_data_free.c
+++ b/src/tree_data_free.c
@@ -139,7 +139,7 @@
 {
     struct lyd_node *iter, *next;
     struct lyd_node *children;
-    struct lyd_node_opaq *opaq;
+    struct lyd_node_opaq *opaq = NULL;
 
     assert(node);