Fix GUILD_ROLE_DELETE triggering ValueError.
Fix GUILD_ROLE_DELETE triggering ValueError.

jhgg/discord.py,Harmon758/discord.py,imayhaveborkedit/discord.py,lgkern/PriestPy,variablehair/Eggplantato,rapptz/discord.py,Harmon758/discord.py,khazhyk/discord.py,mgardne8/discord.py,Rapptz/discord.py,Theoretical/UselessBot