builtin-import: Fix SIGSEGV if no output file is given
builtin-import: Fix SIGSEGV if no output file is given

This patch fixes SIGSEGV if user forgets to give an output filename for 'pstore
import'.

Signed-off-by: Pekka Enberg <add4fcd06328a394f0ad91feda7ee057316dc5ed@kernel.org>

penberg/pstore,penberg/pstore,penberg/pstore,penberg/pstore