Fix runtime error

static/public/js/uiMedia.js

@@ -14,7 +14,8 @@ $(() => {
     }
 
     let setSelectionCheckboxValue = function(media, value) {
-        media.ui.checkbox.checked = value;
+        if (media.ui)
+            media.ui.checkbox.checked = value;
         let indexInSelection = selectedThumbnails.indexOf(media.fixedSum);
         if (value && indexInSelection < 0) {
             selectedThumbnails.push(media.fixedSum);