refs #23111 [finc] provide callback to ajax call options

co-authored by: Robert Lange <robert.lange@uni-leipzig.de>

* covers.js: make selector for spinner less specific

themes/finc/js/covers.js

@@ -22,7 +22,7 @@ function registerCoverForModal(anchor, url) {
 function loadCoverByElement(data, element) {
   var url = VuFind.path + '/AJAX/JSON?method=' + 'getRecordCover';
   var img = element.find('img');
-  var spinner = element.children('div.spinner');
+  var spinner = element.find('.spinner');
   var container = element.children('div.cover-container');
   var anchor = container.children('a.coverlink');
   function coverCallback(response) {
@@ -61,7 +61,7 @@ function loadCoverByElement(data, element) {
     data: data,
     element: element,
     success: coverCallback,
-    error: spinner.hide()
+    error: () => spinner.hide()
   });
 }