libyang MAINTENANCE change format of the empty loops

To improve readability and because of processing by the formatting
tools, add explicit empty block to the empty loops (for, while).
diff --git a/src/validation.c b/src/validation.c
index b5e86d9..316946a 100644
--- a/src/validation.c
+++ b/src/validation.c
@@ -919,7 +919,7 @@
     }
 
     /* find first top-level node */
-    for (tree = node; tree->parent; tree = (struct lyd_node *)tree->parent);
+    for (tree = node; tree->parent; tree = (struct lyd_node *)tree->parent) {}
     while (tree->prev->next) {
         tree = tree->prev;
     }