Bug when trying to sell a book

[HydrogenHL]

I am trying to sell a book using the function "/vendi". The syntax was the following:
"/vendi 9788838699375 25.00"

The result is indeed unexpected, because it returns the following lines:

Mercatino Libri UNICT 📚, [27/03/2024 19:33]
Ricerca del libro associato all'ISBN inserito...

Mercatino Libri UNICT 📚, [27/03/2024 19:33]
Prezzo non valido.

It returned those lines with all the prices I have tried.