Fix missing terminating \0 in rcl_context_impl_t.argv (#969)
Fix missing terminating \0 in rcl_context_impl_t.argv (#969)

Signed-off-by: Haowei Wen <7c2225f767a0a9b289b52152909ab8307bda035e@gmail.com>
ros2/rcl,ros2/rcl