Notice: Trying to get property ‘user_email’ of non-object in /

Hi,
when i use search fonction
some files return these error message:

Notice: Trying to get property ‘display_name’ of non-object in /home/podi123/mysite.com/wp-content/plugins/download-manager/libs/class.Package.php on line 50

Notice: Trying to get property ‘user_email’ of non-object in /home/podi123/mysite.com/wp-content/plugins/download-manager/libs/class.Package.php on line 52

how fix please?
after a google search, i see i m not only…

https://www.google.fr/search?q=Notice:+Trying+to+get+property+%27user_email%27+of+non-object+in+/+download+manager&sxsrf=ALeKk03Qb_TEEFtF7vXn2FvHwqlT7SWc0A:1607961142975&ei=NorXX_39OszjsAfS8q2YCQ&start=0&sa=N&ved=2ahUKEwj98PSF6s3tAhXMMewKHVJ5C5M4ChDy0wN6BAgIED8&biw=1499&bih=812