Bugfix in org-clock-set-current.

Don't try to get the filename as it break `org-clock-set-current' when
trying to clock in from an indirect capture buffer.

lisp/org-clock.el

@@ -1097,9 +1097,7 @@ the clocking selection, associated with the letter `d'."
   "Task currently clocked in.")
 (defun org-clock-set-current ()
   "Set `org-clock-current-task' to the task currently clocked in."
-  (setq org-clock-current-task 
-	(concat (nth 4 (org-heading-components)) 
-		" (" (file-name-nondirectory (buffer-file-name)) ")")))
+  (setq org-clock-current-task (nth 4 (org-heading-components))))
 
 (defun org-clock-delete-current ()
   "Reset `org-clock-current-task' to nil."