Clicking a link on org-agenda buffer invokes org-open-at-point which calls org-element-at-point.

[mr.doojin]

When org-element-at-point is called in org-agenda buffer, a warning is 
displayed.

Warning (org-element): ‘org-element-at-point’ cannot be used in non-Org buffer 
#<buffer *Org Agenda*> (org-agenda-mode)