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/tree_data_helpers.c b/src/tree_data_helpers.c
index e3a090b..b113140 100644
--- a/src/tree_data_helpers.c
+++ b/src/tree_data_helpers.c
@@ -114,7 +114,7 @@
         return NULL;
     }
 
-    for (schema = node->schema; schema->parent; schema = schema->parent);
+    for (schema = node->schema; schema->parent; schema = schema->parent) {}
     return schema->module;
 }