Bug 31297: Allow null value for description in subscription_numberpatterns

Bug 31297: Allow null value for description in subscription_numberpatterns

To test:
1 - Go to Serials
2 - Add a enw subscription
3 - Select Vendor and record, click next
4 - Select Numbring pattern: Number, or any to populate forms
4 - Click 'show advanced pattern'
5 - 'Modify pattern'
6 - Add a new name
7 - 'Save as new pattern'
8 - Nothin happens
9 - Check logs:
    C4::Serials::Numberpattern::AddSubscriptionNumberpattern(): DBI Exception: DBD::mysql::st execute failed: Field 'description' doesn't have a default value at /kohadevbox/koha/serials/create-numberpattern.pl line 58
10 - Apply patch
11 - Update database
12 - Restart all
13 - Click save again
14 - Success!

Signed-off-by: Andrew Fuerste-Henry <andrewfh@dubcolib.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Removed wrong 'out' from atomic update file.

Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>