resellers get an error while checking edit package on the whm.

solution
/usr/local/cpanel/whostmgr/docroot/themes/Xskin
there may be a folder template is missing

so go to /usr/local/cpanel/whostmgr/docroot/themes/another theme and copy the folder template to /usr/local/cpanel/whostmgr/docroot/themes/Xskin.