Bug 17419: Fix smsalertnumber and mobile confusion in moremember.pl

Bug 17419: Fix smsalertnumber and mobile confusion in moremember.pl

members/moremember.pl will set mobile number as smsalertnumber in template if
smsalertnumber is not defined. This will cause incorrect display for SMS number
in patron's Details-tab. This confusion between smsalertnumber and mobile is
already fixed in Bug 14683, but members/moremember.pl was not fixed yet.

This is a minor issue since it won't occur for manually added new patrons due to
fixes already pushed in Bug 14683, but in case patron's smsalertnumber is null
in database, this bug can be replicated:

To test:
1. Set EnhancedMessagingPreferences to "Allow" and make sure SMSSendDriver
   has been set.
2. Add a new patron, give it a mobile/other phone number.
3. Run a SQL query:
   update koha.borrowers set smsalertnumber=NULL where borrowernumber=XXX;
   (replace XXX with your new patron's borrowernumber)
4. Go to patron's details tab and observe that SMS number shows the mobile/
   other phone you provided earlier.
5. Apply patch.
6. Refresh patron's details tab.
7. Observe that smsalertnumber is now empty, as it should be.

Followed test plan, works as expected.
Signed-off-by: Marc <veron@veron.ch>
Signed-off-by: Katrin Fischer  <katrin.fischer@bsz-bw.de>
Signed-off-by: Mason James <mtj@kohaaloha.com>