Update Objects/unicode_writer.c

Co-authored-by: Victor Stinner <vstinner@python.org>

Author: ashm-dev

Objects/unicode_writer.c

@@ -465,8 +465,9 @@ _PyUnicodeWriter_WriteASCIIString(_PyUnicodeWriter *writer,
     if (len == -1)
         len = strlen(ascii);
 
-    if (len == 0)
+    if (len == 0) {
         return 0;
+    }
 
     assert(ucs1lib_find_max_char((const Py_UCS1*)ascii, (const Py_UCS1*)ascii + len) < 128);