use-rs274: must initialize variable file name
use-rs274: must initialize variable file name

side effect of not doing so: files with random names
created each run

Signed-off-by: Jeff Epler <623a871f32baaca066adfe0cac08d7aa7d34027d@unpythonic.net>

ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror