fix(copr): Handle trailing NULL correctly for `concat_ws`. (#6032)
fix(copr): Handle trailing NULL correctly for `concat_ws`. (#6032)

Signed-off-by: Zhu Zihao <ad5962901f35970b4a3ce0f32da943483eaefe1d@163.com>
BusyJay/tikv,BusyJay/tikv,BusyJay/tikv,pingcap/tikv,pingcap/tikv,c4pt0r/tikv,BusyJay/tikv