Invalid arguments are now properly catched and a proper error message is sent (BadUnionArg)

Author: fourjr

CHANGELOG.md

@@ -20,7 +20,8 @@ however, insignificant breaking changes do not guarantee a major version bump, s
 - UnicodeEncodeError will no longer be raised on Windows. ([PR #3043](https://github.com/kyb3r/modmail/pull/3043))
 - Notifications are no longer duplicated when using both `?notify` and `subscribe`. ([PR #3015](https://github.com/kyb3r/modmail/pull/3015))
 - `?contact` now works properly with both category and silent. ([GH #3076](https://github.com/kyb3r/modmail/issues/3076))
-- Resolves `close_on_leave_reason` not properly working when `close_on_leave` is enabled. ([GH #3075](https://github.com/kyb3r/modmail/issues/3075))
+- `close_on_leave_reason` now works properly when `close_on_leave` is enabled. ([GH #3075](https://github.com/kyb3r/modmail/issues/3075))
+- Invalid arguments are now properly catched and a proper error message is sent.
 
 ## Internal
 

bot.py

@@ -1472,7 +1472,7 @@ async def on_error(self, event_method, *args, **kwargs):
         logger.error("Unexpected exception:", exc_info=sys.exc_info())
 
     async def on_command_error(self, context, exception):
-        if isinstance(exception, commands.BadArgument):
+        if isinstance(exception, (commands.BadArgument, commands.BadUnionArgument)):
             await context.trigger_typing()
             await context.send(embed=discord.Embed(color=self.error_color, description=str(exception)))
         elif isinstance(exception, commands.CommandNotFound):