Fix snipe continuation when there's no message content

[Ryan5453]

Traceback (most recent call last):
  File "/home/main/redenv/lib/python3.8/site-packages/discord/ext/commands/core.py", line 85, in wrapped
    ret = await coro(*args, **kwargs)
  File "/home/main/red/cogs/CogManager/cogs/snipe/snipe.py", line 177, in snipe
    description=content[0]
IndexError: list index out of range

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/main/redenv/lib/python3.8/site-packages/discord/ext/commands/bot.py", line 939, in invoke
    await ctx.command.invoke(ctx)
  File "/home/main/redenv/lib/python3.8/site-packages/discord/ext/commands/core.py", line 863, in invoke
    await injected(*ctx.args, **ctx.kwargs)
  File "/home/main/redenv/lib/python3.8/site-packages/discord/ext/commands/core.py", line 94, in wrapped
    raise CommandInvokeError(exc) from exc
discord.ext.commands.errors.CommandInvokeError: Command raised an exception: IndexError: list index out of range

[flaree]

Thanks for the PR!