AutoRoles exception when unused emote is send (AttributeError)

When a unused emote like :crocodile: is send in #bot-spam the exception below accurs. With this a message is send that is not deleted automatically like it should.

app_1    | _ClientEventTask exception was never retrieved
app_1    | future: <ClientEventTask state=finished event=on_message coro=<bound method AutoRolesPlugin.user_role_toggle_by_unicode_emoji of <plugins.auto_roles.AutoRolesPlugin object at 0x7fe07e3f3760>> exception=TypeError("on_error() missing 1 required positional argument: 'error'")>
app_1    | Traceback (most recent call last):
app_1    |   File "/usr/local/lib/python3.8/site-packages/discord/client.py", line 343, in _run_event
app_1    |     await coro(*args, **kwargs)
app_1    |   File "/app/vegas/plugins/auto_roles.py", line 371, in user_role_toggle_by_unicode_emoji
app_1    |     await self._give_role_from_emote_name(message, emote)
app_1    |   File "/app/vegas/plugins/auto_roles.py", line 420, in _give_role_from_emote_name
app_1    |     await self._update_user_role_and_send_embed(role, message)
app_1    |   File "/app/vegas/plugins/auto_roles.py", line 423, in _update_user_role_and_send_embed
app_1    |     if any(role.name == author_role.name for author_role in message.author.roles):
app_1    |   File "/app/vegas/plugins/auto_roles.py", line 423, in <genexpr>
app_1    |     if any(role.name == author_role.name for author_role in message.author.roles):
app_1    | AttributeError: 'NoneType' object has no attribute 'name'
app_1    | 
app_1    | During handling of the above exception, another exception occurred:
app_1    | 
app_1    | Traceback (most recent call last):
app_1    |   File "/usr/local/lib/python3.8/site-packages/discord/client.py", line 348, in _run_event
app_1    |     await self.on_error(event_name, *args, **kwargs)
app_1    | TypeError: on_error() missing 1 required positional argument: 'error'