libyang MAINTENANCE uninitializes variables in optimized code

Silent (probably false positive, but who knows with optimizations)
compiler's warnings (mostly) about uninitialized variables when being
compiled as Release build type.
diff --git a/src/tree_data.c b/src/tree_data.c
index 8e348f6..7a9af79 100644
--- a/src/tree_data.c
+++ b/src/tree_data.c
@@ -1145,7 +1145,7 @@
 lyd_change_meta(struct lyd_meta *meta, const char *val_str)
 {
     LY_ERR ret = LY_SUCCESS;
-    struct lyd_meta *m2;
+    struct lyd_meta *m2 = NULL;
     struct lyd_value val;
     ly_bool val_change;
 
@@ -1374,7 +1374,7 @@
 {
     LY_ERR ret;
     const struct lysc_node *iter = NULL;
-    struct lyd_node *node;
+    struct lyd_node *node = NULL;
     struct lyd_value **dflts;
     LY_ARRAY_COUNT_TYPE u;