Group visibility for SITETREE_GRANT_ACCESS permissions

Make groups visible if member has SITETREE_GRANT_ACCESS permissions, otherwise the dropdown for selecting the group is empty

src/Security/Group.php

@@ -635,6 +635,11 @@ class Group extends DataObject
             return true;
         }
 
+        // if user can grant access for specific groups, they need to be able to see the groups
+        if (Permission::checkMember($member, "SITETREE_GRANT_ACCESS")) {
+            return true;
+        }
+
         return false;
     }