Little bug in config page

I’m using the Pro version since it is a very useful and curated plugin. To help you maintain this high quality, i report you this little bug.
In the configuration page you can leave empty the field
“Enter Number of Attachment Files”
If you leave that field empty, you get errors in the post admin page and you can’t upload any file.
Please, since it seems to be not an option, provide a default number or accept “blank” for “infinite” number.