[SOLVED] An error occurred: Call to a member function has() on null

I just installed edocman and during my first tests to manage searches in PDF documents I came across this error. First I had to give the pdftotext file permission 777 so that it would allow indexing. I loaded the same file a second time (the same file is now displayed twice) and the second time finally shows the indexing (text content). I then wanted to delete the two titles of the list (of the same file) but I get this error.

"An error occurred.
Call to a member function has() on null"

I have tried all the options offered by edocman (Remove Orphan documents/Clean Temporarily folder/Dele documents root path), but I cannot delete the two entries in the document list.

Hi,
Please disable plugin Edocman Dropbox to get the problem resolved.
Thanks
Dam

Thanks for your quick reply! Is it better to uninstall the plugin at this point?