Fix crash on duplicate or out of order reactions.
Fix crash on duplicate or out of order reactions.

Eventual consistency ftw

imayhaveborkedit/discord.py,Harmon758/discord.py,Harmon758/discord.py,mgardne8/discord.py,variablehair/Eggplantato,khazhyk/discord.py,Rapptz/discord.py,rapptz/discord.py