bug#19848: Minibuffer completion does not work with ECB package?

[Angelo Graziosi <angelo.graziosi@alice.it>]

(Following Stefan's suggestion: 
http://lists.gnu.org/archive/html/emacs-devel/2015-02/msg00790.html)

It seems that minibuffer completion does not work properly if ECB
package is installed (from MELPA, with : Options | Manage Emacs 
Packages), and active.

For example, if I want to strip the trailing withe spaces (M-x
delete-trailing-whitespace), I try

   M-x del<TAB>

In the minibuffer I get

Click on a completion to select it.
In this buffer, type RET to select the completion near point.

Possible completions are:
delete-backward-char 	delete-blank-lines
[...]


but at this point, if I click on 'delete-trailing-whitespace', I get

   Minibuffer is not active for completion


If I try to exit with C-G, it print 'Quit', but does not exit. In short,
whatever I do I cannot exit minibuffer if not quitting Emacs.

In the above, if I change 'M-x del<TAB>' with

   M-x dele<TAB>

the completion works,

   M-x delete-

and with few other tabs I can complete the command.

I can reproduce this behavior with this minimal init.el file in ~/.emacs.d:

$ cat init.el
;;
;; ECB : Emacs Code browser setup
;;
(add-to-list 'load-path "~/.emacs.d/elpa/ecb-20140215.114")
(require 'ecb)

;; So that ECB is activated at Emacs startup
(setq ecb-auto-activate t)

;; This is suggested here:
;; http://www.patrickmin.com/linux/tip.php?name=emacs_ecb_startup
(setq ecb-tip-of-the-day nil)
(custom-set-variables '(ecb-options-version "2.40"))

Maybe the issue is in ECB, so I flagged this just for completeness.


TIA,
  Angelo.