Bug 9523: importing staged bib records hangs if a matched bib has been deleted

Bug 9523: importing staged bib records hangs if a matched bib has been deleted

Test Plan:
1) Stage a MARC record file that will have matches with existing records
2) Delete the bib from Koha that was matched on
3) Attempt to import the records into Koha, the import will hang
4) Apply the patch
5) Reload manage-marc-import.pl and attempt to import again, this time it should succeed.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>