Bug 15382: 245$a visibility constraints not respected in opac-MARCdetail.pl

Bug 15382: 245$a visibility constraints not respected in opac-MARCdetail.pl

This tiny change determines if the bibliotitle should be set or not
in accordance with the 'Advanced constraints' visiblity setting for
OPAC.

TEST PLAN
---------
1) Find a record detail in OPAC
2) Click 'MARC view'
   -- 245$a should be visible.
3) In a new tab, log into the staff client
4) Click 'Koha administration'
5) Click 'MARC bibliographic framework'
6) Click 'MARC structure' for the framework of
   the record displayed in OPAC.
7) Search for tag: 245, and click 'Search'
8) Click 'Subfields'
9) Click 'Edit' beside the a subfield.
10) Click 'Advanced constraints'
11) Uncheck 'OPAC'
12) Click 'Save changes'
13) In the OPAC tab, refresh
    -- 245$a (Title) will still be visible!
14) Apply this patch
15) In the OPAC tab, refresh
    -- 245$a (Title) will be hidden.
16) In the staff client, navigate back to
    'Advanced constraints' and check 'OPAC'
17) Click 'Save changes'
18) In the OPAC tab, refresh
    -- 245$a (Title) will be visible again.
19) Run koha qa tools

Signed-off-by: Aleisha <aleishaamohia@hotmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>