bug#728: 23.0.60; flyspell checking is sometimes silently disabled

[Markus Triska]

The error occurs in flyspell-post-command-hook. To reproduce:

1) Install the latest AUCTeX (11.85), and let .emacs consist only of:

   (load "auctex.el" nil t t)

2) Let sat.tex ( http://www.logic.at/prolog/sat.tex ) consist of:

\maketitle
    \includegraphics[scale=0.8]
%       \hline
  
%   \begin{itemize}
%     \hspace{1cm}\hbox{\begin{tabular}
%       $a$ & $b$ & $c$ & $d$ \\

   without leading or trailing whitespace.

3) When you now do:

   $ emacs sat.tex -f flyspell-mode

   and press:

   M-g M-g 3 RET C-s $

   you get:

   Error in post-command-hook: (error Invalid search bound (wrong side
   of point))

   Alternatively, you can also press for example:

   C-n C-n C-p C-n C-n C-n C-n C-n C-n C-p