Don't silently swallow ValueError thrown from on_channel_delete.
Don't silently swallow ValueError thrown from on_channel_delete.

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