Sort by delta broken if sorting on more than one value

If you try to sort first by one value with e.g. delta = 0 and then by another one from the same table with e.g. delta = 1 this fails.

THe problem is in content_handler_sort.inc

This

$this->table_alias = $this->query->ensure_table($this->table, $this->relationship, $join);

Needs to be

$this->table_alias = $this->query->add_table($this->table, $this->relationship, $join);