We run "pre-dump" scripts earlier than calling
anything else, so in case if it get failed the
plugins cleanup routine hit list structure set
into zeros which lead into SIGSEGV when we're
trying to walk over.

Thus simply init it as empty list.
Reported-by: Stanislav Kinsburskiy <skinsbursky@virtuozzo.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>