Please describe the changes this PR makes and why it should be merged:
This PR fixes an edge case where MessageReaction#countDetails was not initialized before a new reaction has been added.
Fixes https://github.com/discordjs/discord.js/issues/10468
Status and versioning classification:
Code changes have been tested against the Discord API, or there are no code changes
I know how to update typings and have done so, or typings don't need updating
Please describe the changes this PR makes and why it should be merged: This PR fixes an edge case where MessageReaction#countDetails was not initialized before a new reaction has been added. Fixes https://github.com/discordjs/discord.js/issues/10468
Status and versioning classification: