Bug 10354 - Don't show optgroup Libraries when no search groups are defined

Bug 10354 - Don't show optgroup Libraries when no search groups are defined

In the OPAC, if there are no search groups defined, there's no reason to
embed library choices inside an <optgroup>. <optgroup> should only be
used to differentiate the list of individual libraries from search
groups. This patch removes the <optgroup> when no search groups are
enabled.

To test, apply the patch and:

- Enable OpacAddMastheadLibraryPulldown.
- Create a library search group in Administration ->
  Libraries and Groups and enable it by checking the "show in search
  pulldown" box.
- View the library pulldown in the OPAC search bar. Libraries and groups
  should be separated into <optgroup>s.
- Disable your library search group and refresh the OPAC page. The
  pulldown of libraries should now display libraries with no <optgroup>.

Signed-off-by: Srdjan <srdjan@catalyst.net.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>