Bug 24957: OpenLibrarySearch shouldnt display if nothing is returned

TO TEST:
1. Turn on OpenLibrarySearch
2. Do an OPAC search that returns results that have results with Open Library results and some that do not.
3. Notice results that return nothing simpliy say "Open Library:" with nothing afterwards.
4. Some results return a png from OpenLibrary or "Not found"
5. Apply patch and look at records again.
6. The results that return nothing for OpenLibrary API should now to hidden.

Signed-off-by: Heather Hernandez <heather_hernandez@nps.gov>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

koha-tmpl/opac-tmpl/bootstrap/js/openlibrary.js

@@ -178,6 +178,8 @@ function default_decorate_el_fn(el, bookdata) {
     }
     if (decoration) {
         el.innerHTML += decoration;
+    } else {
+        el.style.visibility = 'hidden';
     }
 }