[BUG] Incorrect response when only prefix is used

[anf]

Describe the bug
When the user only uses the prefix of the bot, it sort of malfunctions, please see the image for more context.

To Reproduce
Steps to reproduce the behavior:

1. Run an empty command with only the prefix.
2. See error.

Expected behavior
None, as the code is pretty self-explanatory, it handles that, but, it should have a better response.

Screenshots

Additional context
N/A.