Books import - obligatory field?

[S-Haime]

When using the CSV books import function, if the 'pages' field is left blank a server error occurs. (Is the pages field somehow obligatory?)

This is not very user-friendly as this information will not always be entered nor is it logical/intuitive for it to be a required field, as it is non-essential metadata. (If this is not marked as required in the code, there is just an error happening.)

Note: Only tested on playtest, which is slightly more buggy than regular installs. Unable to confirm if it occurs elsewhere.

[S-Haime]

(Note: based on the code, it does seem fine. So it might just be a bug? )