disable gallery action when no images are visible, fixes #620

Closes #620

Merge request studip/studip!1005

resources/assets/javascripts/bootstrap/files.js

@@ -50,6 +50,10 @@ STUDIP.domReady(() => {
     });
 });
 
+$(document).on('files-vue-app-loaded', () => {
+    const lightboxImages = $('.lightbox-image');
+    $('#sidebar-actions a[onclick*="Files.openGallery"]').attr('disabled', lightboxImages.length === 0);
+});
 
 jQuery(document).on('ajaxComplete', (event, xhr) => {
     if (!xhr.getResponseHeader('X-Filesystem-Changes')) {

resources/assets/javascripts/lib/files.js

@@ -31,6 +31,9 @@ const Files = {
                         }
                     },
                     components: { FilesTable, },
+                    mounted () {
+                        $(document).trigger('files-vue-app-loaded');
+                    }
                 });
             });
         }

resources/assets/stylesheets/scss/sidebar.scss

@@ -143,7 +143,8 @@ div#sidebar-navigation {
         box-sizing: border-box;
         line-height: 16px;
     }
-    span[disabled] {
+    span[disabled],
+    a[disabled] {
         color: $dark-gray-color-80;
         cursor: not-allowed;
         font-weight: lighter;