modstruct: struct_calcsize: Fix case of uninitialized var.

py/modstruct.c

@@ -85,7 +85,7 @@ STATIC mp_obj_t struct_calcsize(mp_obj_t fmt_in) {
     char fmt_type = get_fmt_type(&fmt);
     machine_uint_t size;
     for (size = 0; *fmt; fmt++) {
-        uint align;
+        uint align = 1;
         machine_uint_t cnt = 1;
         if (unichar_isdigit(*fmt)) {
             cnt = get_fmt_num(&fmt);