A non-numeric value encountered | WordPress.org

In the course of uploading pics to the gallery following message appears:

Warning: A non-numeric value encountered in /home/.sites/72/site4252024/web/wp-content/plugins/wp-photo-album-plus/wppa-common-functions.php on line 1343 .

Fotos are uploaded, but message appears.

Also frontend upload doesn’t work …

Can you give me a hint what it could be?

• This topic was modified 1 minute ago by Tibor.

The page I need help with: [log in to see the link]