bug#5320: yank-pop does not work in table mode

[harven <harven@free.fr>]

Yank-pop does not work when the cursor is in a cell of a table created
with table mode.

Starting with emacs -Q, create a table (default 3x3)

M-x table-insert RET RET RET RET RET

Then put the cursor in some cell, write a word, kill it, write another word,
kill it again.

word1 M-b C-k word2 M-b C-k

Then try to yank-pop to retrieve the first word

C-y M-y

I get in the minibuffer

Wrong type argument: number-or-marker-p, nil

yank-pop works if the cursor is not in a cell. If I come back in a cell
after yanking outside the table, and try to yank-pop in the cell, no error
is reported but the table is messed up, all cells after the cursor are
destroyed.

In GNU Emacs 22.1.1 (i386-apple-darwin8.10.1, X toolkit)
Also tested in GNU Emacs 23.1 under Debian gnu/linux.