src: silence compiler warning

This commit fixes the following warning:

warning: missing field 'exports' initializer

PR-URL: https://github.com/nodejs/node/pull/28764


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>