Fix AttributeError in log_uncached_deleted_message when channel is None

[oliveman-au]

self.bot.get_channel() can return None if the channel isn't in the bot's cache, but channel.category was being accessed immediately after with no None check, causing an AttributeError.

This is particularly impactful because log_uncached_deleted_message is called for every deleted message that isn't in the cache, which on a large server happens constantly. Every one of those events would silently crash the handler instead of logging.

Added an early return with a trace log if the channel can't be found, matching the pattern used elsewhere in the codebase.

[jb3]

This could probably be a higher log level, we should have some way of seeing how frequently this is happening.

[wookie184]

I believe this is unnecessary as the check is already done in is_channel_ignored:

bot/bot/exts/moderation/modlog.py

Lines 476 to 481 in a04ae25

	if isinstance(channel, int):
	channel = self.bot.get_channel(channel)
	# Ignore not found channels, DMs, and messages outside of the main guild.
	if not channel or channel.guild is None or channel.guild.id != GuildConstant.id:
	return True

It's nice to have this code written in a way that a type checker can understand, but adding a check that will never trigger makes the code less clear.

I would support making this more type checker friendly, but that would need more discussion and I don't think this is the neatest approach so I will close this.