Troublesome extra space in matrix with ConTeXt [closed]

Question

I need to display a column vector in a table and, by doing it, an extra space occurs like an empty extra number. How can I fix this please ?

\starttable[|r|l|]
        \NC     $u=\startmatrix 1 \NR 2 \NR 3 \NR \stopmatrix$
           \NC \type {u=[1;2;3]}        \NC\AR
\stoptable

NB : the code $u=\startmatrix 1 \NR 2 \NR 3 \NR \stopmatrix$ works fine in inline mode. I defined matrix the usual way like this.

\definemathmatrix[matrix]
             [left={\left(\,},
              right={\,\right)},
              align=middle]

I also tried to use \startformula ... \stopformula. in my table but the same extra space occurs...

All ideas are welcome. I use MkIV luatex version of ConTeXt (ubuntu depot version) Thanks.