Fix signing with no password file
Fix signing with no password file

If SWUPDATE_PASSWORD_FILE is not set, passout will have a value of None.
None will be incorrectly used in the signing command.

Set passout to an empty string when SWUPDATE_PASSWORD_FILE isn't set.

Signed-off-by: George McCollister <2dd0a47882f0f6e80e10cdc66eeecff982de281e@gmail.com>
Acked-by: Stefano Babic <2c2905e0c2877c7e4ce40c7425e972302953fda5@denx.de>

sbabic/meta-swupdate,sbabic/meta-swupdate