TypeError: error: Incompatible types in assignment (expression has type "Clan", variable has type "Optional[ForeignKeyFieldInstance[Clan]]")

Describe the bug
Getting a type error when updating the ForeignKey field to a different clan on a Nullable Foreign Key Field instance.

To Reproduce

if await Clan.get_or_none(tag=clantag):
	clan = await Clan.get(tag=clantag)
	if await Player.get_or_none(name=playername):
		if await Season.active_seasons.all().exists():
			await ctx.send("Cannot move players between clans during an active season.")
		else:
			player = await Player.get(name=playername)
			if player.is_enabled():
				player.clan = clan
				await player.save()
				await ctx.send(
					f"Welcome @{playername} to the [{clan.tag}] {clan.name} Clan roster!"
				)
			else:
				player.clan = clan
				await player.save()
				await ctx.send(
					f"Welcome @{playername} to the [{clan.tag}] {clan.name} Clan roster!"
				)
	else:
		await Player.create(name=playername, clan=clan, enabled=True)
		await ctx.send(
			f"Welcome @{playername} to the [{clan.tag}] {clan.name} Clan roster!"
		)
else:
	await ctx.send(f"Clan {clantag} does not exist.")

Expected behavior
This shouldn't error as the code works fine and foreign key field gets updated fine.

Additional context
Add any other context about the problem here.

Start by reproducing the nullable ForeignKey assignment shown in the issue, focusing on assigning a Clan instance to player.clan and then saving the Player. Trace the model and type definitions involved in that field, and verify that static checking accepts the assignment while saving still updates the relation correctly.