Fixes Add Bookmarks in Bookmarks Manager

Resolves brave#7801

Auditors: @bsclifton @darkdh

Test Plan:
- go to Bookmarks Manager
- right click in a bookmarks area (right side)
- select Add bookmark
- bookmark dialog is opened

js/contextMenus.js

@@ -55,6 +55,9 @@ const addBookmarkMenuItem = (label, siteDetail, closestDestinationDetail, isPare
       if (isParent) {
         siteDetail = siteDetail.set('parentFolderId', closestDestinationDetail && (closestDestinationDetail.get('folderId') || closestDestinationDetail.get('parentFolderId')))
       }
+      if (siteDetail.constructor !== Immutable.Map) {
+        siteDetail = Immutable.fromJS(siteDetail)
+      }
       siteDetail = siteDetail.set('location', urlUtil.getLocationIfPDF(siteDetail.get('location')))
       windowActions.setBookmarkDetail(siteDetail, siteDetail, closestDestinationDetail, true)
     }