cp,mv: fix -t DIR option

When the '-t DIR' option is used the loop over the remaining
arguments should terminate when a NULL pointer is reached.

function                                             old     new   delta
mv_main                                              585     590      +5
cp_main                                              492     496      +4
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 9/0)                 Total: 9 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
3 files changed