The following error will occur:
Under the following conditions:
SELECT * FROM xf_attachment
INNER JOIN xf_attachment_data ON xf_attachment.data_id = xf_attachment_data.data_id
INNER JOIN xf_mg_media_item ON xf_attachment.content_id = xf_mg_media_item.media_id
WHERE xf_attachment.content_type = 'xfmg_media'
AND xf_attachment_data.width = 0
AND xf_mg_media_item.media_type = 'image'
Under normal circumstances this condition should never occur, but on a forum I help on this happened. The file system had the correct PDF file, but somehow the database table had it as an image with 0 width. This caused the server error which running the watermark rebuild process.
