Problem with documents management

Hi,
when i put a document in my projeqtor non problem. When i would download this document, without error but any result. In logs i have this message:
2016-03-29 11:48:23.051 ***** ERROR ***** ERROR *****
2016-03-29 11:48:23.051 ***** ERROR ***** on file '/var/www/html/tool/jsonList.php' at line (383)
2016-03-29 11:48:23.051 ***** ERROR ***** cause = Trying to get property of non-object
2016-03-29 11:48:27.507 ***** ERROR ***** ERROR *****

I use PostgreSQL database.

Thanks.
Bruno.