alsactl: load_state: Only delete config if one was loaded

alsactl: load_state: Only delete config if one was loaded

If load_configuration fails with open_failed == true, load_state will
jump to the out label without config being initialized and pass this
uninitialized config value to snd_config_delete. This commit fixes this
issue by initializing config with NULL and checking if it is non-null
before invoking snd_config_delete.

Fixes: https://github.com/alsa-project/alsa-utils/pull/94
Fixes: f138117 ("alsactl: load_state() - initialize config variable for the open_failed case")
BugLink: https://github.com/alsa-project/alsa-utils/issues/93
Signed-off-by: Sören Tempel <soeren+git@soeren-tempel.net>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>