How to advice `evil-delete'

[York Zhao]

Hi,

I've been straggling with this for the entire afternoon and am really really
frustrated. What I want is that when deleting an empty line, I don't want it to
be yanked, just delete.

So I adviced `evil-delete' like this and it worked as I expected.

(defadvice evil-delete
  (around around-delete (beg end type register yank-handler) activate)
  (if (eq type 'line)
	  (let (here)
		(save-excursion
		  (goto-char beg)
		  (skip-chars-forward " \n\t" end)
		  (setq here (point)))
		(if (eq here end)
			(flet ((evil-yank (&rest args) t))
			  ad-do-it)
		  ad-do-it))
	ad-do-it))

However, as soon as I add another advice on `evil-yank', things stopped working
correctly, even thougt the yank advice is empty like the following, things still
not working properly.
	
(defadvice evil-yank
  (around around-yank (beg end type register yank-handler) activate)
  ad-do-it)

The problem is that after I deleted an empty line, I could no longer yank
anything, whenever I yank I get the errer:

Debugger entered--Lisp error:
(wrong-type-argument commandp evil-yank)
call-interactively(evil-yank nil nil)

Could anybody give me some idea of where the problem is? Am I supposed to advice
these "special" operator functions and is there anything "special" in advicing
them?

Thanks in advace,

York