bug#9733: 24.0.90; inadvertent paste during mouse-2 spell correction with flyspell-mode

[emacs user]

1) start from Emacs -Q

2) C-x m to open a new mail message, (this problem occurs in other
modes as well,
such as auctex)

3) insert the following sentence:

here is a sentence with a mistaake

4) M-x flyspell-mode, the word mistaake is highlighted.

5) double click on "sentence" and then click once to un-highlight it.

6) mouse-2 on mistaake, choose the correct spelling "mistake" from the memu.

Consequence: mistaake is replaced with missentecetake, that is,
mouse-2 does both yank and spell correction instead of only spell
correction.

while the above is reproducible for me, I found this problem to occur
during normal worth with emacs in most cases but not all.

In GNU Emacs 24.0.90.2 (x86_64-apple-darwin11.1.0, NS apple-appkit-1138.00)
 of 2011-10-04 on udp003013uds
Windowing system distributor `Apple', version 10.3.1138
configured using `configure  '--with-ns' '--without-x''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: C
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t