[Koha] Software error at the time of checkin

[Vimal Kumar V.]

Dear Friends,
I got following error message when checkin a book,
Software error:
Can't call method "truncate" on an undefined value at
/usr/share/koha/lib/C4/Circulation.pm line 1966.
For help, please send mail to the webmaster ([no address given]), giving
this error message and the time and date of the error.

Version of Koha is 3.20.1
Ubuntu 14.04.

Request guidance to solve this problem.
Regards,

-- 
Vimal Kumar V.
Technical Assistant
Mahatma Gandhi University Library
Kottayam, Kerala- 686 560
Web: http://www.vimalkumar.info
Blog: http://linuxhalwa.blogspot.com http://kohageek.blogspot.in
http://moovandan.blogspot.in
---------------------------------------------------------------------------
"I forget what I was taught. I only remember what I have learnt"
-Patrick White