(sponsors): Allow prompt to be nullable.

bot/modules/sponsors/module.py

@@ -15,11 +15,12 @@ sponsored_commands = {'profile', 'stats', 'weekly', 'monthly'}
 @LionContext.reply.add_wrapper
 async def sponsor_reply_wrapper(func, ctx: LionContext, *args, **kwargs):
     if ctx.cmd and ctx.cmd.name in sponsored_commands:
-        sponsor_hint = discord.Embed(
-            description=ctx.client.settings.sponsor_prompt.value,
-            colour=discord.Colour.dark_theme()
-        )
-        if 'embed' not in kwargs:
-            kwargs['embed'] = sponsor_hint
+        if (prompt := ctx.client.settings.sponsor_prompt.value):
+            sponsor_hint = discord.Embed(
+                description=prompt,
+                colour=discord.Colour.dark_theme()
+            )
+            if 'embed' not in kwargs:
+                kwargs['embed'] = sponsor_hint
 
     return await func(ctx, *args, **kwargs)