Added check at C level that rollends is correct type and length.
Added check at C level that rollends is correct type and length.

vlulla/data.table,Rdatatable/data.table,jangorecki/data.table,Rdatatable/data.table,jangorecki/data.table,Rdatatable/data.table,vlulla/data.table,jangorecki/data.table,Rdatatable/data.table,jangorecki/data.table,vlulla/data.table,vlulla/data.table