Hi everyone,

I have this frequent error (but not always), when I'm in the org agenda
view trying to clock in the task under cursor. Here's a stack trace:

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  org-agenda-clock-in(nil)
  funcall-interactively(org-agenda-clock-in nil)
  call-interactively(org-agenda-clock-in nil nil)
  command-execute(org-agenda-clock-in)

Note, every time this occurs, I can refresh the agenda view, then clock in
with no problems.  But this refreshing gets tiring..

Any help?  I'm using org-plus-contrib-20171106, Emacs 25.3.2.

Thanks,
Zongheng